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DEPARTMENT  OF  THE  INTERIOR 

UNITED  STATES  GEOLOGICAL  SURVEY 

GEORGE  OTIS  SMITH,  Director 


Bulletin  445 


GEOLOGY  OF  THE  PEGMATITES  AND 
ASSOCIATED  ROCKS  OF  MAINE 

INCLUDING 

FELDSPAR,  QUARTZ,  MICA,  AND 
GEM  DEPOSITS 


BY 

EDSON  S.  BASTIN 


WASHINGTON 

GOVERNMENT  PRINTING  OFFICE 
1911 


Digitized  by  the  Internet  Archive 
in  2015 


https://archive.org/details/geologyofpegmati4434bast 


CONTENTS. 


Introduction 

Definition  of  pegmatite 

Geographic  distribution 

Geology 

Bordering  rocks 

Pegmatites  in  foliated  rocks 

General  statement 

Sedimentary  foliates 

Igneous  foliates 

Pegmatites  in  massive  granites 

Age 

General  character 

Mineral  and  chemical  composition 

Mineral  constituents 

Relative  proportions  of  minerals 

Quartzose  phases 

Fluidal  cavities 

Sodium  and  lithium  phases 

Muscovite  phase 

Texture 

Irregularity  of  grain 

Graphic  granite 

Feldspar  brushes 

Intergrowths  of  minor  constituents. . . 

Mica 

Gem-bearing  pegmatites 

Origin  of  the  Maine  pegmatites... 

Relations  to  granites 

External  conditions 

Dominant  constituents 

Minor  constituents 

Gaseous  constituents 

Viscosity  and  gas  content 

Miarolitic  cavities 

Contact-metamorphic  effects 

Forms  of  the  intrusives 

Temperatures  of  pegmatite  crystallization 
Experiments  of  Wright  and  Larsen. . . 

Application  to  Maine  pegmatites 

Eutectics  in  pegmatites 

Mineralogical  provinces 

Geographic  relations 

Summary 


Page. 

9 

10 

10 

10 

10 

11 

11 

11 

12 

13 

15 

15 

15 

15 

18 

18 

19 

20 
22 
22 
22 
22 
23 

25 

26 
26 
27 

27 

28 
28 

29 

30 
32 

32 

33 

35  . 

36 
36 
39 
39 
43 
43 
45 


3 


4 


CONTENTS. 


Page. 

Local  descriptions 46 

Androscoggin  County 46 

Auburn 46 

Character  and  distribution  of  the  pegmatites 46 

Auburn  Falls 46 

Auburn  reservoir 46 

Danville  Corners 47 

Danville  Junction 48 

Mount  Apatite 49 

Quarries 50 

Maine  Feldspar  Company  quarry  and  mill 50 

Turner  feldspar  quarries 54 

Towne  feldspar  and  gem  quarry 55 

Wade  and  Pulsifer  gem  quarries 56 

Minot 59 

Poland 59 

Cumberland  County 61 

Brunswick 61 

Westbrook 62 

Hancock  County 63 

Lincoln  County 63 

Edgecomb 63 

Edgecomb  feldspar  quarry 63 

Geologic  relations 64 

Boothbay  Harbor 64 

Character  and  relations  of  the  pegmatites 64 

Schists  associated  with  pegmatites 68 

Syenite  porphyry 69 

Oxford  County 70 

Albany 70 

French  Mountain  beryl  locality 70 

Bennett  mica  prospect 70 

Pingree  mica  prospect 70 

Andover 71 

Buckfield 71 

Greenwood 71 

Hebron 72 

Hibbs  feldspar  and  mica  mine 72 

Mount  Rubellite 74 

Streaked  Mountain ’ 74 

Mills  feldspar  quarry 75 

Newry 76 

Norway 78 

Paris 79 

Hill  north  of  Crocker  Hill 79 

Mount  Mica 81 

History 81 

Gem-bearing  zone 83 

Pockets 85 

Minerals 86 

Gems 89 

Production  and  method  of  mining 92 

Peru 93 


CONTENTS. 


5 


Local  descriptions — Continued. 

Oxford  County — Continued.  Page. 

Rumford 93 

Vicinity  of  Rumford  Falls 94 

Black  Mountain  mica  mine 95 

Standish 98 

Stoneham 98 

Geology 98 

Gem  localities 98 

Sugar  Hill 99 

Harndon  Hill 100 

Stow 102 

Waterford 102 

South  Waterford  mica  mine 103 

Beech  Hill  mica  mine 104 

Sagadohoc  County 105 

Georgetown 105 

Georgetown  Center 105 

Hinckleys  Landing 105 

Goldings  feldspar  quarry 105 

Small  Point  feldspar  quarry 108 

Schist-pegmatite  contacts  on  Bay  Point  Peninsula 108 

Topsham ; 109 

Distribution  of  the  quarries 109 

Products  of  the  quarries 110 

Mount  Ararat  feldspar  quarries 110 

Fisher’s  feldspar  quarry 112 

William  Willes  feldspar  quarry 1 113 

Maine  Feldspar  Company’s  quarry 115 

G.  D.  Willes  feldspar  quarry 115 

North  Topsham  feldspar  quarry 116 

Mill  of  Trenton  Flint  and  Spar  Company 117 

Vicinity  of  Topsham  village 117 

Economically  important  pegmatite  minerals 119 

Feldspar 119 

Potash-soda  feldspars 119 

Lime-soda  feldspars  or  plagioclases 120 

Graphic  granite 124 

Mining 125 

Commercial  availability  of  deposits 126 

Milling 127 

Uses 129 

Grades  and  prices 130 

Production 132 

Quartz 133 

General  statement 133 

Massive  crystalline  quartz 133 

Occurrence 133 

Milling 133 

Uses 134 

Production 136 

Prices 137 

Smoky  quartz 137 

Rose  quartz 137 

Amethyst 138 


6 


CONTENTS. 


Economically  important  pegmatite  minerals — Continued.  Page. 

Mica 138 

Types 138 

Physical  and  chemical  properties 139 

Occurrence 140 

Mining  and  manufacture 141 

Uses 141 

Prices  and  production 142 

Tourmaline 143 

Chemical  and  physical  properties 143 

Occurrence 143 

Mining,  prices,  etc 144 

Beryl 144 

Chemical  and  physical  properties 144 

Opaque  beryl 145 

Emerald 145 

Aquamarine 146 

Golden  beryl 146 

Cgesium  beryl 147 

Topaz 147 

Index 149 


ILLUSTRATIONS. 


Page. 

Plate  I.  Map  of  southern  and  eastern  Maine,  showing  distribution  of  granites 
and  allied  rocks  and  locations  of  developed  pegmatite  de- 
posits  In  pocket. 

II.  Microphotograph  of  fine-grained  pegmatite  from  Lewiston 10 

III.  A,  Highly  inclined  dike  of  pegmatite  on  schists  at  Pemaquid  Point; 

B,  Flat-lying  or  sill-like  dike  in  pegmatite  in  bed  of  Androscoggin 
River,  Auburn-Lewiston 10 

IV.  A,  Injection  gneiss,  McMahon  Island;  B,  Injection  gneiss,  George- 

town  10 

V.  A,  Lenses  of  quartz  diorite  in  porphyritic  granite*  St.  George  River; 

B , Flow  gneiss,  same  locality 12 

VI.  Zone  of  strain,  fracture,  and  recrystallization  in  rose  quartz  from 

Norway 18 

VII.  Graphic  intergrowth  of  microcline  and  quartz,  Auburn 22 

VIII.  Photomicrograph  of  graphic  granite  from  Topsham 24 

IX.  A,  Muscovite-rich  zones  in  pegmatite,  Topsham;  B,  Pocket  in  peg- 
matite, Mount  Mica 26 

X.  A,  Deflection  of  schist  folia  near  pegmatite,  Paris;  B,  Development 

of  feldspar  crystals  in  schist  near  pegmatite,  Rumford  Falls 34 

XI.  General  view  of  Mount  Mica  tourmaline  mine 82 

XII.  Early  workings  at  Mount  Mica 84 

XIII.  Largest  pocket  in  pegmatite  at  Mount  Mica 86 

XIV.  Largest  crystal  of  tourmaline  ever  found  at  Mount  Mica 88 

XV.  Large  single  tourmaline  from  Mount  Mica 90 

XVI.  A,  Diabase  dike  network,  Stoneham;  B,  Quartz  dike  in  pegmatite, 

South  Glastonbury,  Conn 98 

XVII.  Microphotograph  of  thin  section  of  feldspar  from  Golding’s  Sons’ 

quarry,  Georgetown 120 

XVIII.  Intergrowths  of  feldspar  and  quartz 124 

XIX.  Muscovite  from  Topsham,  showing  wedge  structure 138 

Figure  1.  Pinch  and  swell  structure  in  pegmatite  dike 11 

2.  Gradation  of  granite  into  pegmatite,  Boothbay  Harbor 14 

3.  Quartz  offshoot  from  pegmatite,  Paris 19 

4.  Fluidal  cavities  in  pegmatitic  quartz 20 

5.  Diagram  showing  composition  of  graphic  granite 40 

6.  Relations  of  pegmatite  and  wall  rock  at  Hibbs  feldspar  and  mica 

mine,  Hebron 73 

7.  Fluidal  cavities  in  spodumene  from  Newry 77 

8.  Diagram  showing  geologic  structure  at  Mount  Mica  tourmaline 

mine,  Paris 84 


7 


GEOLOGY  OF  THE  PEGMATITES  AND  ASSOCIATED 
ROCKS  OF  MAINE. 


By  Edson  S.  Bastin. 


INTRODUCTION. 

The  field  studies  which  form  the  basis  of  this  report  were  made  by 
the  writer  during  July  and  August,  1906,  under  the  general  supervision 
of  George  Otis  Smith,  of  the  United  States  Geological  Survey.  The 
writer  wishes  to  acknowledge  the  valuable  advice  and  kindly  assistance 
of  the  late  Prof.  Leslie  A.  Lee,  state  geologist  of  Maine,  at  the  time  the 
field  work  for  this  report  was  done,  and  the  cordial  cooperation  of 
many  persons  interested  in  the  deposits  concerned,  without  whose 
aid  these  studies  would  not  have  been  possible. 

The  expenses  of  the  work  were  shared  equally  by  the  Survey  Com- 
mission of  the  State  of  Maine  and  the  United  States  Geological 
Survey. 

On  account  of  the  brief  time  at  the  writer’s  disposal  in  the  field, 
it  was  impossible  to  attempt  anything  like  a prospecting  of  the  whole 
State  for  the  minerals  here  considered.  Visits  were  made,  however, 
to  nearly  all  of  the  localities  which  had  been  or  are  at  the  present  time 
operated  commercially,  and  numerous  observations  were  made  on 
the  geology  of  the  intervening  territory. 

With  the  exception  of  a few  of  the  gem  deposits,  most  of  the  minerals 
here  described  have  been  exploited  commercially  only  within  the  past 
fifty  years.  They  belong  neither  to  that  class  of  natural  resources, 
such  as  coal  and  limestone,  which  are  useful  to  a pioneer  civilization, 
nor  (with  the  exception  of  the  gems)  to  the  class  of  highly  precious 
materials  which  attract  the  explorer  or  the  adventurer.  Their  utili- 
zation was  possible  only  after  a very  considerable  development  in  the 
arts  and  industries  of  New  England  had  taken  place. 


9 


10 


PEGMATITES  AND  ASSOCIATED  ROCKS  OF  MAINE. 


DEFINITION  OF  PEGMATITE. 

The  granite-pegmatites,  in  which  are  found  feldspar,  quartz,  mica, 
and  gem  minerals,  are  composed  of  the  same  mineral  constituents  as 
the  ordinary  granites  of  the  State,  and  differ  from  these  principally 
in  their  greater  coarseness  and  in  their  very  uneven  texture. 

Among  themselves  the  granite-pegmatites  differ  greatly  in  coarse- 
ness, some  being  little  coarser  than  ordinary  coarse-grained  granite 
and  others  showing  single  masses  of  feldspar  or  of  quartz  20  feet  in 
diameter.  Their  distinguishing  feature  is,  therefore,  not  coarseness 
of  grain  but  extreme  irregularity  of  grain.  In  a granite  different 
grains  of  the  same  mineral  species  differ  in  size,  but  usually  only 
within  rather  narrow  limits.  In  a pegmatite,  on  the  other  hand, 
they  appear  to  differ  without  limit,  a crystal  of  feldspar  an  inch 
across  perhaps  having  a neighbor  which  is  several  feet  across.  This 
textural  feature  is  illustrated  on  a microscopic  scale  in  Plate  II,  which 
is  a reproduction  of  a photomicrograph  of  fine-grained  aplitic  pegma- 
tite exposed  in  the  river  bed  at  Lewiston. 

Pegmatite  usually  forms  dikes  or  sill-like  masses  in  areas  occupied 
principally  by  rocks  of  other  kinds.  (See  p.  11.) 

GEOGRAPHIC  DISTRIBUTION. 

Pegmatites  occur  throughout  the  Appalachian  Mountain  region 
from  Alabama  to  New  York  and  thence  northeastward  into  Connecti- 
cut, Massachusetts,  New  Hampshire,  and  Maine.  In  most  of  these 
States  they  have  been  worked  commercially  to  a greater  or  less 
extent.  In  Maine  the  commercial  deposits  are  confined  largely  to 
Cumberland,  Sagadahoc,  Lincoln,  Androscoggin,  and  Oxford  counties, 
though  pegmatites  also  occur  to  some  extent  in  Franklin,  Kennebec, 
Waldo,  Knox,  Hancock,  and  Washington  counties.  Their  general 
distribution,  as  well  as  that  of  the  granites,  is  shown  on  Plate  I,  on 
which  are  also  indicated  the  localities  which  have  been  worked 
commercially  for  various  pegmatite  minerals. 

Excellent  opportunities  for  studying  the  character  and  relationships 
of  the  pegmatites  are  afforded  by  many  of  the  quarry  openings,  by 
numerous  glaciated  rock  surfaces,  and  by  almost  continuous  exposures 
along  the  seashore.  The  shore  in  the  Boothbay  region  especially  is 
an  excellent  field  for  study. 

GEOLOGY. 

BORDERING  ROCKS. 

The  geologic  relations  of  the  Maine  pegmatites  show  that  most 
of  them  are  distinctly  intrusive  into  the  surrounding  rocks,  although 
the  conditions  of  intrusion  are  somewhat  varied;  and  that  in  origin 
they  are  closely  connected  with  the  granites  (p.  27).  The  rocks 


U.  S.  GEOLOGICAL  SURVEY 


BULLETIN  445  PLATE  II 


MICROPHOTOGRAPH  OF  FINE-GRAINED  PEGMATITE  FROM  RIVER  BED  AT  LEWISTON 
MAGNIFIED  ABOUT  34  TIMES. 


Illustrates  the’ extreme  irregularity  characteristic  of  the  commonest  type  of  pegmatitic  texture. 


U.  S.  GEOLOGICAL  SURVEY 


BULLETIN  445  PLATE  III 


A.  HIGHLY  INCLINED  DIKE  OF  PEGMATITE  IN  SCHISTS  AT  PEMAQUID  POINT,  MAINE. 
Showing  characteristic  swelling  and  pinching  of  dikes. 


B.  FLAT-LYING  OR  SILL-LIKE  DIKE  IN  PEGMATITE  INTRUDING  GENTLY  INCLINED 
SEDIMENTARY  SCHISTS.  BED  OF  ANDROSCOGGIN  RIVER,  BETWEEN  RAILWAY 
AND  HIGHWAY  BRIDGES,  AU  BURN-LEW  I STON,  MAINE. 


Showing  lenslike  form  characteristic  of  many  of  these  pegmatite  masses. 


U.  S.  GEOLOGICAL  SURVEY 


BULLETIN  445  PLATE  IV 


A.  INTIMATE  INJECTION  OF  SEDIMENTARY  SCHISTS  BY  PEGMATITE,  FORMING  AN 
INJECTION  GNEISS. 

South  shore  of  McMahon  Island. 


B.  PEGMATITE  MASS,  SENDING  OFF  STRINGERS  OF  PEGMATITE  AND  QUARTZ  INTO  THE 
BORDERING  SCHIST  AND  THUS  FORMING  AN  INJECTION  GNEISS. 


Bay  Point  Peninsula,  Georgetown. 


GEOLOGY. 


11 


into  which  they  are  intruded  are  in  some  places  granites,  but  are 
generally  foliates, a either  schist  or  gneiss.  The  foliates  are  in  many 
places  dynamically  metamorphosed  sediments,  but  in  others  are 
unquestionably  primary. 

PEGMATITES  IN  FOLIATED  ROCKS. 


General  statement. — Though  showing  minor  irregularities  of  form, 
most  of  the  pegmatite  masses  in  the  foliated  rocks  are  of  sheetlike 
character  and  lie  parallel  or  nearly  parallel  to  the  schist  or  gneiss 
folia.  If  the  foliates  are  steeply  inclined  the  pegmatite  exhibits  a 
dikelike  form  (PL  III,  A);  if  they  are  flat-lying  the  pegmatite  mass 
assumes  a sill-like  form  (PI.  Ill,  B). 

Another  feature  highly  characteristic  of  pegmatite  masses  in 
foliates  is  their  tendency  to  swell  and  thin  along  tlieir  trend  so  as  to 
form  virtually  a series  of  connected  len  tide's.  (See  fig.  1.) 

, The  contact  between  pegmatite  and  foliate  is  in  nearly  all  areas 
very  sharp,  whether  the  pegmatite  lies  parallel  to  or  cuts  across 
the  folia  and  whether  its 
mass  is  large  or  small. 

In  many  places  (see  PI. 

IV,  A,  B)  the  pegmatitic 
intrusion  is  so  intimate 
that  the  bordering  schist 
becomes  an  injection 
gneiss.  Such  gneisses 
are  very  characteristic  features  of  many  districts  in  southern  Maine, 
particularly  in  Oxford  County. 

Sedimentary  foliates. — The  sedimentary  origin  of  many  of  the  foli- 
ates associated  with  the  pegmatites  is  shown  beyond  question  at  a 
number  of  localities  by  the  preservation  of  distinct  bedding  in  the 
more  quartzose  layers.  Notable  examples  are  the  schists  exposed 
at  the  Graphite  mine  at  Crocker  Hill  (near  Paris)  and  at  many 
places  in  Auburn  village  and  studied  particularly  at  the  new  reser- 
voir site,  where  the  layers  in  which  bedding  is  preserved  are  shown 
on  microscopic  study  to  be  micaceous  quartzite. 

Since  the  pegmatite  frequently  cuts  across  the  folia  of  the  sedi- 
mentary schists  and  does  not  notably  change  the  latter  along  the 
contacts,  it  is  plain  that  the  foliation  of  the  schists  is  not  a con- 
tact effect  of  the  pegmatite  intrusion.  It  is  to  be  attributed  mainly 
to  regional  metamorpliism  previous  to  the  pegmatite  intrusions. 
Since  these  foliates  bear  no  traces  of  fossils,  their  age  is  indetermi- 
nate, but  certain  of  them  may  be  correlated  with  the  Penobscot  for- 


Figure  1.— Pinch  and  swell  structure  in  pegmatite  dike. 


a The  term  “foliates”  was  proposed  by  the  writer  (Jour.  Geology,  vol.  17,  p.  449)  as  a convenient  compre- 
hensive term  to  include  all  rocks  showing  foliated  structures  other  than  bedding  planes,  fts  use  avoids 
frequent  repetition  of  the  terms  schists  and  gneisses,  and  avoids  any  postulate  as  to  the  primary  or  second- 
ary character  of  the  foliated  structure. 


12 


PEGMATITES  AND  ASSOCIATED  ROCKS  OF  MAINE. 


mation  of  the  Penobscot  Bay  region.®  As  the  last  great  dynamic 
metamorphism  which  affected  southern  and  central  Maine  took  place 
probably  near  the  close  of  Ordovician  time,  these  dynamically  meta- 
morphosed sediments  are  probably  not  younger  than  Ordovician. 

Igneous  foliates. — Others  of  the  foliated  rocks  with  which  the  peg- 
matites are  associated  are  probably  primary  or  flow  foliates;  that  is, 
igneous  rocks  that  owe  their  foliated  structure  to  differential  move- 
ment within  their  mass  before  complete  solidification.  To  this  class 
probably  belong  many  of  the  foliates  in  the  Boothbay  Harbor  region 
and  about  Brunswick  and  Topsham.  Many  of  them  are  very  similar 
in  their  general  appearance  to  foliates  of  sedimentary  origin  but 
upon  microscopic  study  are  found  to  be  indistinguishable  in  mineral 
composition  from  igneous  rocks.  One  of  the  most  instructive  expo- 
sures of  a foliate  of  this  type  occurs  on  the  east  shore  of  St.  George 
River,  near  the  extreme  southern  edge  of  the  Rockland  quadrangle, 
where  porpliyritic  granite  of  normal  composition,  with  feldspar 
phenocrysts  from  one-half  to  three-fourths  of  an  inch  in  length,  con- 
tains a number  of  elongated  parallel  lenses  of  much  finer  grained  rock 
of  dioritic  composition.  (See  PL  V,  A.)  The  largest  of  these  lenses 
is  about  6 feet  long  and  1 foot  wide.  The  inclosing  granite  shows 
a decided  grain  parallel  to  the  direction  of  elongation  of  the  lenses, 
and  in  other  similar  occurrences  in  this  region  the  feldspar  pheno- 
crysts of  the  bordering  granite  show  a tendency  toward  orientation 
with  their  long  axes  parallel  to  the  axes  of  the  basic  lenses.  Within 
a few  rods  of  this  exposure  occurs  another  which  presents  the  appear- 
ance shown  in  Plate  V,  B,  the  light-colored  bands  having  about  the 
texture  and  composition  of  normal  granite  and  the  darker  bands 
being  quartz  diorite  similar  to  the  lenses  at  the  exposure  shown  in 
Plate  V,  A. 

Under  the  microscope  the  dioritic  and  granitic  bands  are  both 
seen  to  be  feldspatliic  and  of  interlocking  granular  texture  without 
any  cataclastic  structures.  The  basic  bands,  however,  besides  being 
finer  grained  than  the  others,  contain  a much  larger  percentage  of 
green  hornblende  and  a smaller  percentage  of  quartz.  Both  phases 
contain  abundant  titanite  in  grains,  many  of  which  show  well-defined 
crystal  form.  The  feldspar  in  both  has  the  composition  of  oligoclase- 
andesine. 

It  seems  evident  that  the  gneiss  of  Plate  V,  B,  represents  merely 
the  next  step  of  the  process  of  combined  flowage  and  magmatic 
differentiation  which  developed  the  relations  shown  in  Plate  V,  A, 
and  that  the  two  represent  two  stages  in  the  making  of  a flow  gneiss. 
At  the  time  when  the  whole  mass  was  in  a molten  condition  the 
basic  portions  were  presumably  more  fluid  than  the  acidic  portions, 
and  the*process  is  probably  to  be  regarded  as  an  intimate  intrusion  of 

a Penobscot  Bay  folio  (No.  149),  Geol.  Atlas  U.  S.,  U.  S.  Geol.  Survey,  1907. 


U.  S.  GEOLOGICAL  SURVEY 


BULLETIN  445  PLATE  V 


A.  LENSES  OF  QUARTZ  DIORITE  IN  PORPHYRITIC  GRANITE.  PROBABLY  THE  RESULT  OF 
COMBINED  FLOWAGE  AND  BASIC  SEGREGATION  ABOUT  MANY  CENTERS. 

East  shore  of  St.  George  River,  near  south  border  of  Rockland  quadrangle. 


B.  COARSE  IGNEOUS  GNEISS  OF  ALTERNATE  LAYERS  OF  GRANITE  AND  QUARTZ  DIORITE. 
Same  locality.  Showing  a further  step  in  the  process  illustrated  above. 


GEOLOGY. 


13 


the  more  viscous  by  the  less  viscous  portions  of  the  same  magma 
when  both  were  under  lateral  compression. 

At  an  old  road-metal  quarry  in  the  city  of  Brunswick  schists  of 
probable  igneous  origin  are  also  well  exposed  in  association  with 
pegmatite.  The  schists  show  very  even  and  regular  foliation  and  an 
alternation  of  broad  light-gray  layers  with  narrower  ones  which  are 
dark  gray  to  nearly  black.  The  lighter  bands  are  seen  under  the 
microscope  to  be  a hornblende  granite  of  interlocking  granular 
texture  and  without  cataclastic  structures.  The  foliated  structure 
is  due  to  a greater  abundance  of  hornblende  along  certain  planes 
than  along  others  and  to  subparallel  elongation  of  the  hornblende 
grains.  The  dark-gray  phases  of  the  schist  have  the  mineral  com- 
position of  quartz  diorite,  the  feldspar  being  largely  andesine.  A 
few  bands  up  to  one-eighth  inch  or  so  across  are  a more  coarsely 
crystalline  association  of  quartz  with  a little  feldspar.  These  schists 
carry  none  of  the  minerals,  such  as  staurolite  and  andalusite,  fre- 
quently observed  in  metamorphosed  sediments,  and  though  their 
derivation . by  metamorphism  from  arkoses  or  graywackes  is  con- 
ceivable it  is  not  probable.  The  pegmatite  associated  with  these 
schists  locally  cuts  across  their  foliation,  but  in  other  places  grades 
into  them  so  completely  as  to  suggest  that  the  schist  was  not  com- 
pletely solidified  at  the  time  the  pegmatite  was  intruded. 

Here  and  at  a number  of  other  localities  a slight  foliation  parallel 
to  the  schist  folia  is  visible  in  some  of  the  pegmatites;  it  suggests  a 
slight  flowing  movement  in  the  schist  subsequent  to  the  intrusion  of 
the  pegmatite.  The  thickening  of  the  schist  folia  opposite  the  nodes 
of  pegmatite  dikes  and  their  thinning  opposite  the  bulges  (see  fig.  1) 
is  also  indicative  of  flowing  movements  in  the  schists  at  the  time  the 
pegmatite  was  intruded.  Many  of  the  pegmatite  bodies  associated 
with  the  primary  flow  foliates  are  probably  to  be  regarded  as  intru- 
sions under  high  pressure  of  a less  viscous  into  a more  viscous  magma. 

PEGMATITES  IN  MASSIVE  GRANITES. 

The  relationships  exhibited  at  a number  of  localities  between  the 
pegmatites  and  the  granites  throw  much  light  on  the  origin  of  the 
former.  Of  broad  significance  is  the  fact  that  granite  is  present  in 
all  of  the  districts  in  which  pegmatite  occurs.  The  reverse  relation 
also  holds,  though  to  a lesser  degree.  The  similarity  in  mineral 
composition  between  the  granites  and  the  pegmatites  will  be  con- 
sidered later. 

The  detailed  relationships  existing  between  the  two  rocks  are 
various.  At  the  Woodside  quarry  in  the  town  of  Brunswick,  2J 
miles  southeast  of  Hillside  station,  a rather  fine-grained  muscovite- 
biotite  granite  has  been  quarried  for  flagging  and  underpinning.  In 
it  the  pegmatite  often  forms  lens-shaped  or  wholly  irregular  bodies, 


14  PEGMATITES  AND  ASSOCIATED  KOCKS  OF  MAINE. 

the  two  rocks  being  characterized  by  the  same  minerals  and  grading 
into  each  other  in  the  most  gradual  and  complete  manner.  In  such 
cases  there  can  be  no  question  that  the  two  rocks  crystallized  from 
the  same  magma  and  that  the  pegmatitic  masses  are  to  be  regarded 
as  segregations  within  the  granite.  In  other  places,  however,  even 
at  this  same  quarry,  pegmatite,  which  in  general  appearance  and 
mineral  composition  is  indistinguishable  from  that  described  above, 
forms  sharp-walled  dikes  in  the  granite. 

An  exposure  on  the  shore  of  the  first  point  west  of  Boothbay 
Harbor  shows  a dike  of  fine-grained  granite  1J  feet  wide  cutting 
schist  and  pegmatite.  A few  feet  farther  north  the  same  granite 
dike  is  itself  cut  by  pegmatite  that  is  wholly  similar  in  appearance 
to  the  pegmatite  which  the  granite  intrudes.  These  relations  show 
that  the  pegmatites  are  not  precisely  contemporaneous.  Since, 

however,  there  is  no  evi- 
dence here  or  elsewhere 
in  Maine  of  very  wide 
divergence  in  the  age  of 
different  pegmatites  or 
different  granites  (see 
p.  15),  the  exposure  also 
shows  the  broad  con- 
temporaneity of  granite 
and  pegmatite. 

On  the  island  of  South- 
port,  on  the  shore  near 
the  south  entrance  of 
Townsend  Gut,  the 
schist,  granite,  and  peg- 
matite are  associated  in 

Figure  2. — Gradation  of  granite  into  pegmatite,  Boothbay  Harbor.  , . 

the  manner  shown  m 
figure  2.  Both  are  distinctly  intrusive,  the  schist  contacts  being 
everywhere  sharp  and  in  many  places  very"  ragged.  The  main  mass 
of  the  intrusion  is  granite  of  normal  texture,  but  the  narrower  branches 
sent  off  by  the  granite  parallel  to  the  foliation  of  the  schists  become 
typical  pegmatite  a short  distance  from  the  granite  mass.  The 
gradation  between  the  two  rocks  is  gradual  and  complete. 

Under  the  microscope  the  granite  shows  an  interlocking  granular 
texture  and  consists  principally  of  quartz  and  microcline,  with  minor 
amounts  of  orthoclase,  of  biotite  altering  to  chlorite,  and  of  mus- 
covite, in  part  primary  and  in  part  a product  of  feldspar  alteration. 
Micrographic  granite  is  present  in  small  amounts,  as  are  scattered 
small  grains  of  oligoclase.  The  minerals  of  the  pegmatite  are  iden- 
tical with  those  of  the  granite  but  occur  in  much  larger  crystals, 


MINERAL  AN  j CHEMT 


COMPOSITION. 


15 


with  much  greater  range  in  siz-  g individuals  of  the  same  mineral 

species.  Oligoclase  and  microg  *phic  intergrowths  of  quartz  and 
feldspar  are  also  more  abundant  in  the  pegmatite  than  in  the  granite. 

For  detailed  descriptions  of  other  instances  of  gradations  or  close 
relationship  between  granite  and  pegmatite  the  reader  is  referred 
to  locality  descriptions  of  the  Rumford  Falls  region  (p.  94),  Stow 
(p.  102),  Edgecomb  (p.64),  Boothbay  Harbor  (p.  67),  and  the  South 
Waterford  mica  mine  (p.  103). 

The  granites  and  associated  pegmatites  are  the  youngest  known 
rocks  occurring  in  notable  abundance  within  the  State.  Here  and 
there,  however,  they  are  cut  by  younger  small  dikes  of  diabase, 
usually  aphanitic  and  sharp  walled.  Usually  these  occur  only  as 
individuals,  but  on  the  shore  of  Keewaydin  Lake  (Lower  Stone 
Pond),  near  the  village  of  East  Stoneham,  schist  and  associated 
pegmatite  are  intruded  by  a remarkable  network  of  fine-grained 
diabase.  (See  PL  XVI,  A.) 

AGE. 

The  field  studies  in  Maine  have  afforded  no  evidence  of  great 
diversity  in  age  among  the  pegmatite  deposits.  Although  all  of 
them  are  not  strictly  contemporaneous,  it  seems  probable  that  all 
were  formed  within  the  limits  of  a single  period  of  geologic  time. 
As  it  has  been  shown  (p.  27)  that  the  pegmatites  are  broadly  con- 
temporaneous with  the  granites  with  which  they  are  invariably 
associated,  the  age  of  the  pegmatites  may  be  inferred  from  that  of 
the  granites. 

The  evidence  thus  far  available  indicates  that  all  of  the  granites 
of  the  State  are  of  approximately  the  same  geologic  age.  In  the 
Penobscot  Bay  region  granite  is  intrusive  in  rocks  of  Silurian  (Niag- 
aran)  age.a  In  the  Perry  Basin,6  in  the  extreme  eastern  part  of  the 
State,  granite  pebbles  are  absent  from  the  late  Silurian  sediments 
but  are  present  in  the  conglomerate  of  the  Perry  formation,  which 
is  probably  of  Upper  Devonian  age.  The  granites  were  therefore 
intruded  in  late  Silurian  or  in  Devonian  time,  and  the  pegmatites  are 
also  probably  of  that  age. 

GENERAL  CHARACTER. 

MINERAL  AND  CHEMICAL  COMPOSITION. 

Mineral  constituents. — The  pegmatite  deposits  in  all  parts  of  the 
State  show  great  similarity  in  their  principal  minerals,  although 
exhibiting  notable  differences  in  their  minor  constituents.  Essen- 
tially they  are  coarse  granites,  their  principal  light-colored  con- 
stituents being  potash  and  soda  feldspars,  quartz,  and  muscovite, 

a Penobscot  Bay  folio  (No.  149),  Geol.  Atlas  U.  S.,  U.  S.  Geol.  Survey,  1907. 

b Smith,  G.  0.,  and  White,  David,  Geology  of  the  Perry  Basin:  Prof.  Paper  U.  S.  Geol.  Survey  No.  35, 

1905. 


16 


PEGMATITES  AND  ASSOCIATED  ROCKS  OF  MAINE. 


and  their  principal  dark-colored  constituents  black  mica  (biotite) 
and  black  tourmaline.  In  pegmatites  in  which  black  mica  is  abun- 
dant black  tourmaline  is  almost  always  rare  or  absent,  and  vice  versa. 
Accessory  constituents  present  in  almost  all  pegmatites  are  garnet, 
magnetite,  and  green  opaque  beryl.  Accessory  minerals  present 
only  in  certain  pegmatites  number  over  fifty  species,  the  most 
important  probably  being  lepidolite  or  lithium  mica;  amblygonite; 
spodumene;  blue,  green,  and  pink  tourmaline;  transparent  green, 
pale-blue,  or  golden  beryl;  colorless  to  amber-colored  topaz;  and 
rose  and  amethystine  quartz. 

The  following  minerals  have  been  reported  from  the  pegmatite 
deposits  of  Maine : 

Albite. — Common  in  many  of  the  pegmatite  deposits;  in  some  places  massive,  but 
usually  occurring  as  the  white  lamellar  variety  clevelandite.  Especially  abundant  in 
gem-bearing  pegmatites. 

Allanite. — Reported  from  pegmatite  at  Mount  Apatite,  in  Auburn. 

Amblygonite. — An  original  constituent  of  many  of  the  pegmatite  deposits,  espe- 
cially those  bearing  gem  minerals. 

Apatite. — Occurs  as  an  original  pegmatite  constituent  wholly  inclosed  by  other 
minerals  in  many  pegmatite  deposits.  The  fine  purple  apatites  of  Mount  Apatite, 
in  Auburn,  occur  on  the  walls  of  pockets  and  were  probably  deposited  by  aqueous  or 
pneumatolytic  agencies  during  the  latest  stages  of  the  pegmatite  crystallization. 

Arsenopyrite. — Reported  from  pegmatite  at  Mount  Rubellite,  in  Hebrop. 

Autunite. — Occurs  at  the  Dunton  tourmaline  mine  in  Newry,  Oxford  County,  in 
crystals  seldom  over  A-  inch  across,  embedded  in  or  lying  between  plates  of  cleve- 
landite. Mostly  decomposed.  Found  also  at  Harndon  Hill,  in  Stoneham. 

Bertrandite. — Occurs  with  herderite  and  hamlinite  in  cavities  in  pegmatite  at 
Stoneham. 

Beryl. — Translucent  to  opaque  varieties,  wholly  inclosed  by  other  constituents, 
occur  m nearly  all  the  coarser  pegmatite  bodies.  A few  crystals  reach  gigantic  pro- 
portions. In  a few  coarse  pegmatites  transparent  pale-green  gem  varieties  (aqua- 
marine) occur  completely  embedded  or  projecting  from  the  walls  of  cavities. 

Beryllonite. — Not  found  in  place,  but  occurring  in  the  soil  in  Stoneham.  It  is 
attached  to  typical  pegmatite  minerals  and  is  plainly  an  original  pegmatite  constit- 
uent. 

Biotite. — One  of  the  abundant  constituents  of  most  of  the  pegmatites. 

Calcite. — Not  observed  as  an  original  pegmatite  constituent,  but  occurs  occasionally 
as  a secondary  deposit  in  fissures  and  cavities. 

Cassiterite. — An  original  constituent  in  pegmatite  at  Paris,  Hebron,  Stoneham,  and 
Auburn. 

Childrenite. — Reported  as  an  original  constituent  of  pegmatite  at  Mount  Rubellite, 
in  Hebron,  occurring  in  minute  hair-brown  prismatic  crystals  with  amblygonite. 

Chrysoberyl. — An  original  pegmatite  constituent  at  a large  number  of  localities, 
though  nowhere  abundant. 

Clevelandite. — See  Albite. 

Columbite.— An  original  constituent  of  certain  pegmatites.  Present  only  in  small 
amounts. 

Cookeite. — Abundant  as  a coating  in  most  of  the  pockets  in  the  coarser  pegmatites. 
Not  an  original  constituent  but  secondary  and  due  to  water  deposition. 

Damourite. — Occurs  at  Mount  Rubellite,  in  Hebron,  as  an  alteration  product  of  tour- 
maline. Also  reported  from  Mount  Apatite,  in  Auburn. 


MINERAL  AND  CHEMICAL  COMPOSITION. 


17 


Emerald. — Gem  beryl  found  in  Maine  is  usually  so  pale  that  it  is  classed  as  aquama- 
rine. One  fractured  crystal  found  by  the  writer  at  the  Dunton  mine  in  Newry  could 
properly  be  classed  as  a pale  emerald. 

Feldspar. — One  of  the  principal  pegmatite  minerals.  See  albite,  orthoclase,  and 
microcline. 

Fluorite. — Small  crystals  occur  as  an  original  constituent  in  a few  of  the  pegmatites, 
but  in  general  fluorite  is  much  rarer  in  the  Maine  pegmatites  than  in  those  of  certain 
other  regions. 

Garnet. — A common  constituent  of  most  of  the  pegmatites.  Frequently  occurs  in 
graphic  intergrowth  with  quartz,  muscovite,  or  feldspar.  Garnet  of  gem  clearness  is 
extremely  rare. 

Graphite. — Absent  from  most  of  the  Maine  pegmatites.  Occurs  in  pegmatite 
injected  into  sedimentary  schists  at  a few  localities. 

Gummite. — Reported  in  minute  particles  from  pegmatite  at  Mount  Apatite,  in 
Auburn.  An  alteration  product  of  some  uranium  mineral. 

Halloysite. — Reported  from  Mount  Mica.  Probably  a decomposition  product  of 
feldspar. 

Hamlinite. — Occurs  sparingly  at  Stoneham,  associated  with  herderite  and  ber- 
trandite. 

Eehronite. — See  Amblygonite. 

Herderite. — Found  at  Stoneham,  Me.,  on  quartz  crystals  in  pockets  in  the  pegmatite. 
Found  sparingly  in  Hebron  and  Greenwood,  at  Mount  Apatite  in  Auburn,  and  at 
Berry’s  quarry  in  Poland. 

Kaolinite. — A decomposition  product  of  feldspar.  Common  in  pockets  in  the 
coarser  pegmatites. 

Limonite. — A secondary  mineral  in  some  pegmatites,  resulting  from  the  decomposi- 
tion of  other  iron-bearing  minerals. 

Lepidolite. — Common  in  pegmatites  which  bear  gem  tourmalines. 

Lollingite. — Occurs  in  narrow  stringers  cutting  feldspar  at  Mount  Mica,  in  Paris,  as 
an  original  pegmatite  constituent. 

Magnetite. — Common  in  many  pegmatites  in  well-developed  step-crystals. 

Microcline. — One  of  the  commonest  constituents  in  the  pegmatites.  Most  of  the 
potash  feldspar  present  is  microcline  rather  than  orthoclase. 

Mica. — See  Biotite,  Muscovite,  and  Lepidolite. 

Molybdenite. — Abundant  as  an  original  constituent  in  granite  and  associated  pegma- 
tite at  Catherine  Hill  in  Hancock  County,  and  reported  in  small  amounts  in  similar 
rocks  elsewhere.  Reported  from  pegmatite  in  Auburn.  Rare  in  most  pegmatite 
bodies. 

Montmorillonite. — Associated  with  cookeite  and  other  secondary  minerals  in  the  pock- 
ets of  several  of  the  coarser  pegmatite  masses.  A product  of  feldspar  decomposition. 

Muscovite. — One  of  the  principal  constituents  in  nearly  all  pegmatites. 

Orthoclase. — Present  with  microcline  in  nearly  all  of  the  pegmatites,  the  two  being 
commonly  intergrown  in  the  same  crystal. 

Phenacite. — Reported  from  pegmatite  at  Noyes’s  tourmaline  mine  in  Greenwood. 

Plumbago. — See  Graphite. 

Pollucite. — Occurs  in  pockets  in  pegmatite  at  Mount  Rubellite  in  Hebron. 

Pyrite. — An  original  constituent  in  many  Maine  pegmatites. 

Pyrrhotite. — An  original  pegmatite  constituent  at  Mount  Mica,  in  Paris,  and  at  a few 
other  localities. 

Quartz. — White  or  gray;  one  of  the  principal  constituents  of  all  the  pegmatites. 
Massive  rose  quartz  occurs  in  a few  places  and  crystal  groups  of  amethystine  and 
smoky  quartz  are  developed  here  and  there  on  the  walls  of  pockets  in  the  pegmatite. 

Rhodochrosite. — An  original  pegmatite  constituent  at  the  Towne  quarry  in  Auburn. 

63096°— Bull.  445—11—2 


18 


PEGMATITES  AND  ASSOCIATED  ROCKS  OF  MAINE. 


Schorl. — See  Tourmaline. 

Spinel. — Reported  from  pegmatite  at  Cobble  Hill  in  Norway. 

Spodumene. — Common  in  many  of  the  coarser  pegmatites,  especially  those  that  carry 
gem  tourmalines,  lepidolite,  and  other  lithium  minerals. 

Titanite. — A minor  original  constituent  of  many  of  the  pegmatites. 

Topaz. — An  original  constituent  of  a few  of  the  coarser  pegmatites.  Usually  forms 
crystals  on  the  walls  of  cavities.  A massive  constituent  of  some  of  the  solid  peg- 
matites. 

Tourmaline. — Schorl  or  black  tourmaline  is  a common  constituent  of  many  of  the 
pegmatites.  Colored  tourmalines  occur  in  some,  in  many  places  completely  inclosed 
by  other  minerals,  but  in  others  implanted  on  the  walls  or  lying  on  the  floors  of  cavities. 

Triphylite. — An  original  pegmatite  mineral  at  Harndon  Hill  in  Stoneham.  Asso- 
ciated with  spodumene  in  Peru. 

Triplite. — An  original  constituent  of  pegmatite  in  Auburn  and  Stoneham.  Present 
only  in  small  amounts. 

Vesuvianite. — Reported  from  pegmatite  at  Mount  Rubellite  in  Hebron. 

Yttrocerite. — Reported  from  pegmatite  at  Mount  Mica,  in  Paris. 

Zircon. — Reported  from  pegmatite  in  Auburn  and  Norway  and  from  Mount  Mica,  in 
Paris. 

Relative  proportions  of  minerals. — Not  only  are  a great  variety  of 
minerals  present  in  the  pegmatites,  but  there  is  also  much  variability 
in  their  relative  proportions.  In  the  vast  majority  of  deposits  the 
pegmatite  minerals  appear  to  be  present  in  very  nearly  the  same  pro- 
portions as  in  the  associated  granites.  Variations  in  their  proportions 
are  principally  along  two  lines,  the  first  involving  an  increase  in 
silica,  the  pegmatite  becoming  more  quartzose;  and  the  second 
involving  an  increase  in  both  sodium  and  lithia,  the  pegmatite  becom- 
ing rich  in  albite  (variety  clevelandite)  and  in  the  lithium  minerals, 
lepidolite,  spodumene,  colored  tourmaline,  and  amblygonite.  A 
minor  variation  involving  an  increase  in  the  fluorine  content  is  shown 
by  the  presence  of  the  fluorine  minerals  topaz,  fluorite,  herderite, 
hamlinite,  certain  types  of  apatite,  etc.  Increase  in  soda  and  lithium 
and  increase  in  fluorine  are  both  usually  accompanied  by  some  increase 
in  the  phosphorus  content.  Cavities  which  were  probably  originally 
filled  with  water  are  more  abundant  in  the  soda-lithium  rich  pegma- 
tites than  in  the  normal  pegmatites.  As  shown  later,  the  magmas 
from  which  the  former  solidified  were  presumably  more  aqueous  than 
those  of  the  normal  pegmatites. 

Quartzose  phase. — The  first  type  of  variation,  increase  in  the  quartz 
content,  is  not  as  common  a phenomena  in  Maine  as  in  certain  other 
regions  where  pegmatites  are  abundant,  and  it  commonly  takes  place 
on  a small  scale  only.®  Quartzose  phases  of  the  pegmatite  are  par- 
ticularly well  shown  on  a nearly  bare  hilltop  2\  miles  northeast  of 
Paris  in  Oxford  County,  where  the  pegmatite  is  cut  by  a number  of 
quartz  veins  or  dikes  mostly  under  6 inches  wide  and  mostly  parallel 
to  a rather  poorly  defined  system  of  joints  in  the  pegmatite.  Some 


<*  Certain  large  quartz  dikes  may  be  genetically  connected  with  the  pegmatite  magmas.  Such  connec- 
tion nas  not  as  yet,  however,  been  proved. 


U.  S.  GEOLOGICAL  SURVEY 


BULLETIN  445  PLATE  VI 


ZONE  OF  STRAIN,  FRACTURE,  AND  RECRYSTALLIZATION  IN  ROSE  QUARTZ  FROM  NORWAY, 

MAINE. 


Magnified  about  34  diameters.  Shows  the  continuance  of  certain  of  the  straight  bands  of  inclusions  from 
the  unstrained  quartz  into  the  strained  zone. 


MINERAL  AND  CHEMICAL  COMPOSITION. 


19 


of  these  quartz  veins  possess  very  sharp  boundaries,  but  others  are 
only  vaguely  delimited  from  the  pegmatite.  The  quartz  veins  of  the 
latter  type  are  particularly  likely  to  contain  scattered  crystals  of 
orthoclase-microcline  and  some  .muscovite  and  black  tourmaline. 
Black  tourmaline  is  also  in  some  of  the  veins  associated  with  quartz 
alone,  the  two  minerals  being  in  many  places  intimately  intergrown. 
In  some  narrow  veins  the  black  tourmaline  may  be  more  abundant 
than  the  quartz.  In  one  place  the  genetic  relation  between  a quartz 
vein  and  the  pegmatite  was  shown  in  the  unequivocal  manner 
illustrated  in  figure  3.  Contemporaneous  quartz  dikes  in  pegmatite 
are  also  well  exposed  in  the  Boothbay  Harbor  region.  (See  p.  166.) 

At  a large  number  of  localities,  where  injection  gneisses  are  associ- 
ated with  pegmatite,  quartz  stringers  in  the  gneiss  can  be  traced  into 
continuity  with  the  pegmatite.  A striking  instance  of  this  is  illus- 
trated in  Plate  IV,  B. 

In  the  Maine  deposits  quartz  is  very  rarely  found  in  distinct  bands 
in  dikes  or  sills  of  pegmatite.  In  a 
single  small  dike  in  Topsham  some 
concentration  of  quartz  in  the  cen- 
tral portion  of  the  dike  was  ob- 
served, the  feldspar  being  concen- 
trated mainly  along  the  walls. 

Four  thin  sections  of  rose,  white, 
and  gray  quartz  from  the  larger 
quartz  masses  in  the  pegmatites 
were  examined  under  the  micro- 
scope. One  of  these  consisted  of 
a single  quartz  individual,  but  the 
other  three  showed  several  inter- 

locking  quartz  grains  within  the  ri0URE  3._Quartz  ofIshoot  trom  pegmatite, 

small  area  covered  by  the  micro-  Paris,  Me. 

scope  slide.  The  quartz  in  all  of  these  showed  little  or  no  strain 
except  along  an  occasional  zone  of  fracturing  and  recrystallization 
such  as  that  shown  in  Plate  VI.  In  one  specimen  of  quartz  from  a 
quartz-rich  pegmatite  near  Cumberland  Mills  (see  p.  62)  all  of  the 
grains  are  much  strained  and  are  granulated  along  their  borders. 
Like  the  development  of  mica-coated  shear  planes  in  certain  pegma- 
tites, this  indicates  slight  local  shearing  movements  subsequent  to 
some  of  the  pegmatite  crystallization.  Such  phenomena  are  the 
exception,  however,  and  not  the  rule. 

Fluidal  cavities. — Fluidal  cavities  of  microscopic  dimensions  are 
abundant  in  most  of  the  pegmatite  quartz  examined.  They  are  very 
similar  in  character  in  almost  all  the  quartzes,  characteristic  forms 
being  shown  in  figure  4.  Nearly  all  contain  a vacuole  or  gas  bubble, 
which  in  the  larger  cavities  reverses  its  position  in  the  cavity  when  the 


20 


PEGMATITES  AND  ASSOCIATED  ROCKS  OF  MAINE. 


slide  is  rotated  in  a vertical  plane,  moving  always  slowly  toward  the 
top  of  the  cavity  and  thus  indicating  that  the  vacuole  is  of  lower 
density  than  the  inclosing  fluid.  An  examination  of  a number  of  thin 
sections  of  Maine  granites  shows  that  the  inclusions  in  the  quartzes 
of  both  pegmatites  and  granite  are  similar  in  character  and  distribu- 
tion and  are  not  noticeably  different  in  abundance.  In  both  types 
of  rocks  the  fluidal  cavities  are  generally  arranged  in  bands,  most  of 
which  are  nearly  straight,  though  some  are  wavy.  Some  of  these 
bands  terminate  abruptly  at  the  border  of  a quartz  grain,  but  others 
pass  without  change  or  deflection  from  one  quartz  grain  to  another. 

In  the  rose  quartz 
illustrated  in  Plate  VI 
some  of  the  bands  of 
fluid  inclusions  in  the 
larger  quartz  grains 
terminate  abruptly  at 
the  sheared  and  re- 
crystallized zone  and 
others  continue  into 
it.  Bands  of  inclu- 
sions also  pass  from 
grain  to  grain  within 
the  sheared  zone.  It 
appears  therefore  that 
some  of  the  bands  of 
inclusions  are  not  only 
later  than  the  original 
crystallization  of  the 
quartz  but  are  later 
even  than  the  strain- 
ing, granulation,  and 
r e cr  y stallization 
which  subsequently 

Figure  4— Fluidal  cavities  in  pegmatitic  quartz,  X 360.  affected  it. 

The  tint  and  degree  of  opacity  exhibited  by  the  quartz  seems  to 
be  dependent  in  some  measure  on  the  abundance  and  distribution  of 
the  inclusions.  In  several  pieces  of  dirty-gray,  opaque  quartz, 
inclusions  were  particularly  abundant  and  were  not  confined  to  bands 
but  were  also  scattered  irregularly  through  the  quartz.  A thin  sec- 
tion of  transparent  smoky  quartz  from  the  Berry  quarry  in  Poland 
was  seen  under  the  highest  available  power  of  the  microscope  (540 
diameters)  to  be  clouded  with  inclusions  so  minute  that  their  char- 
acter could  not  be  made  out.  They  were  not  arranged  in  bands  and 
the  usual  type  of  fluidal  cavities  was  entirely  absent.  It  is  not 
uncommon  for  the  inclusions  in  pegmatite  quartzes  to  be  in  two 
dominant  sets  of  bands  nearly  at  right  angles  to  each  other  and 


MINERAL  AND  CHEMICAL  COMPOSITION. 


21 


showing  considerable  uniformity  of  trend  throughout  the  area  of  the 
thin  section.  A thin  section  of  an  intergrowth  of  quartz  and  garnet 
from  Mount  Apatite  showed  well-developed  bands  of  inclusions 
in  both  minerals,  though  the  bands  were  most  abundant  and  regular 
in  the  quartz.  The  inclusions  appeared  to  be  of  the  same  type  in 
both,  but  none  were  observed  to  pass  from  one  mineral  to  the  other. 
Alternating  bands  of  clear  and  opaque  quartz  conspicuous  to  the 
unaided  eye  in  the  quartz  of  certain  pegmatites  are  due  to  the  much 
greater  abundance  of  fluidal  cavities  in  the  opaque  areas. 

Dale®  reports  fluidal  cavities  ranging  from  0.00285  to  0.062 
millimeter  in  Redstone,  N.  H.,  granite.  Fluid  inclusions  in  the 
quartz  and  garnet  intergrowth  described  above  ranged  from  0.0015 
to  0.0068  millimeter.  Those  in  the  quartz  of  fine-grained  granite 
associated  with  pegmatite  at  Rumford  Falls  ranged  from  0.0015  to 
0.01  millimeter  in  diameter.  In  the  associated  pegmatite  from  the 
same  locality  inclusions  similar  in  character  occurred  in  bands  and 
showed  the  same  range  in  size.  In  both  of  the  Rumford  Falls  rocks 
the  bands  of  inclusions  in  the  quartz  terminate  abruptly  against 
bordering  feldspars.  In  the  latter  mineral  no  fluidal  cavities  were 
observed. 

Sodium  and  lithium  phases. — Increase  in  the  proportions  of  sodium 
and  lithium  in  the  pegmatites  results  in  the  formation,  in  regions 
where  most  of  the  pegmatite  is  of  normal  character,  of  a few  bands'  or 
zones  characterized  by  the  presence  of  clevelandite,  lepidolite, 
spodumene,  and  colored  tourmalines  in  addition  to  the  more  common 
pegmatite  minerals.  The  rich  tourmaline-bearing  pegmatites  of 
Mount  Mica  and  Mount  Apatite  are  of  this  type.  Increase  in  the 
phosphorus  content  is  shown  by  the  presence  of  amblygonite  in  nearly 
all  such  deposits.  The  sodium  and  lithium  rich  pegmatites  are 
confined  almost  exclusively  to  the  western  part  of  Androscoggin 
County  and  to  the  central  and  eastern  part  of  Oxford  County;  prac- 
tically all  occur  within  a radius  of  30  miles  from  Mount  Mica,  the 
richest  discovered  locality.  Although  it  is  true  that*the  pegmatites 
within  this  area  are  richer  than  the  normal  pegmatites  in  sodium  and 
lithium  their  average  composition  is  but  slightly  different,  since 
even  within  this  area  the  sodium  and  lithium  rich  phases  constitute 
only  a small  proportion  of  the  total  mass  of  the  pegmatite. 

Fluorine  phase. — Some  sodium  and  lithium  rich  pegmatites  carry 
fluorine  minerals,  but  pegmatites  carrying  fluorine  and  phosphorus 
minerals  alone  in  addition  to  the  normal  pegmatite  constituents  are 
confined  largely  to  the  western  part  of  Oxford  County.  Even  there 
they  constitute  but  a small  proportion  of  the  total  mass  of  pegmatite 
present. 

a Dale,  T.  N.,  Commercial  granites  of  Massachusetts,  New  Hampshire,  and  Rhode  Island:  Bull  U.  S. 
Geol.  Survey  No.  354, 1908,  p.  42. 


22 


PEGMATITES  AND  ASSOCIATED  ROCKS  OF  MAINE. 


Muscovite  phase.— A few  deposits  showing  local  increases  in  the 
proportion  of  muscovite  have  been  worked  for  this  mineral  in  the 
past,  but  have  not  been  commercially  successful. 

TEXTURE. 

The  pegmatites  show  remarkable  differences  in  coarseness,  some, 
especially  the  narrower  dikes  and  sills,  being  but  little  coarser  than 
medium-grained  granites,  though  differing  strikingly  from  the  latter 
in  texture,  and  others  containing  single  crystals  of  nearly  pure 
feldspar  20  feet  across  and  single  beryl  crystals  the  diameter  of  a 
hogshead.  The  majority  of  the  deposits  are  nearer  the  lower  limit 
than  the  higher.  Only  the  coarsest  deposits  are  commercially 
valuable  for  their  feldspar,  quartz,  mica,  or  gem  minerals,  and  these 
constitute  a relatively  small  percentage  of  the  total  mass  of  pegmatitic 
material  present  in  any  district.  In  most  of  the  pegmatites  worked 
commercially  the  feldspar  and  quartz  crystals  will  not  average  more 
than  4 or  5 feet  in  diameter. 

Irregularity  of  grain. — The  most  striking  characteristic  of  the  tex- 
ture of  the  pegmatites,  with  the  exception  of  the  graphic  intergrowths 
described  below,  is  their  irregularity.  Typical  granites  show  consid- 
erable uniformity  in  the  size  of  grains  of  the  same  mineral  species, 
but  the  pegmatites  show  no  such  regularity,  a feldspar  crystal,  for 
example,  being  as  likely  to  be  two  or  three  or  even  ten  times  as  large 
as  an  adjacent  crystal  as  to  be  of  equivalent  size.  This  feature  is 
shown  on  a microscopic  scale  in  Plate  II. 

Graphic  granite. — Most  of  the  pegmatites  contain  much  graphic 
granite,  formed  by  an  intimate  intergrowth  or  interpenetration  of 
large  single  crystals  of  quartz  and  feldspar.  In  certain  directions 
through  these  intergrowths  the  quartz  forms  an  angular  pattern 
somewhat  resembling  the  cuneiform  inscriptions  of  the  ancients.  (See 
PI.  XVIII.)  Fine-grained  phases  pass  in  the  most  gradual  manner  into 
coarser  graphic  granite  (PI.  VII) ; and  the  latter,  by  decrease  in  the 
percentage  of  qhartz,  may  pass  into  masses  of  pure  feldspar,  or  by  de- 
crease in  the  percentage  of  feldspar  into  masses  of  pure  quartz.  Much 
of  the  material  mined  as  “spar”  is  coarse-grained  graphic  granite 
containing  from  10  to  20  per  cent  of  free  quartz. 

On  casual  inspection  the  coarser  types  of  graphic  granite  appear 
to  contain  a somewhat  larger  proportion  of  feldspar  than  the  finer- 
grained  types.  Chemical  analyses  of  graphic  granites  of  different 
coarseness  from  Maine  and  from  other  districts  indicate,  however, 
that  the  proportion  of  feldspar  to  quartz  bears  no  marked  relation 
to  the  coarseness.  Such  variations  as  do  occur  are  within  relatively 
narrow  limits  and  appear  to  be  dependent  on  the  composition  of 
the  feldspar  and  on  other  factors  not  yet  understood.  Analyses 
of  graphic  granites  of  widely  different  coarseness  from  the  Fisher 


GEOLOGICAL  SURVEY 


mSmB- 


GRAPHIC  INTERGROWTH  OF  MICROCLINE  AND  QUARTZ  OF  GRADUALLY  VARYING  COARSENESS. 
Mount  Apatite,  Auburn.  From  specimen  in  U.  S.  National  Museum. 


28 


T-EXTURE. 

feldspar  quarry  in  Topsham  are  given  on  page  124.  In  the  quarry 
these  two  rocks  graded  gradually  into  one  another,  and  as  shown 
by  the  analyses  the  proportion  of  feldspar  to  quartz  is  nearly 
identical  in  both.  The  samples  analyzed  were  obtained  by  grinding 
five  or  six  pounds  of  each  granite  and  quartering  down  the  product 
to  a quantity  convenient  for  analysis.  Some  allowance  must,  of 
course,  be  made  for  the  difficulty  in  procuring  a sample  that  is  truly 
representative  of  the  rock  mass.  This  difficulty  was  greater  in  the  case 
of  the  coarser  rock. 

Feldspar  “brushes.” — A very  uncommon  type  of  graphic  granite 
was  observed  only  in  Topsham,  in  the  G.  D.  Willes  feldspar  quarry, 
where  it  was  exposed  on  the  extreme  southern  wall  in  dikelike  bands 
in  the  normal  pegmatite  up  to  a foot  or  so  in  width.  These  bands 
appear  to  the  unaided  eye  to  consist  largely  of  buff-colored  feldspar 
with  different  though  minor  amounts  of  biotite.  The  feldspar  forms 
an  aggregate  of  brush-shaped  or  long  fan-shaped  crystals  placed  with 
their  long  axes  at  right  angles  to  the  general  trend  of  the  dikelike 
band.  A faint  banding  in  these  layers  parallel  to  their  general  trend 
and  at  right  angles  to  the  trend  of  the  feldspar  brushes  somewhat 
simulates  bedding. 

This  banding  is  the  combined  effect  (1)  of  a greater  abundance  of 
biotite  along  certain  layers  than  along  others;  (2)  of  the  presence  of 
zones  quite  even  in  width,  characterized  by  a coarser  intergrowth 
of  feldspar  and  quartz  than  the  adjacent  layers,  though  generally 
showing  crystallographic  continuity  from  one  layer  to  another  and 
even  into  a third  layer;  and  (3)  of  the  presence  of  some  parting  along 
planes  parallel  to  the  a pinacoid  and  resulting  slight  clouding  of  the 
feldspar  by  alteration  along  these  fractures. 

Single  feldspar  brushes  range  in  length  from  a fraction  of  an  inch 
to  3 inches.  The  biotite  forms  thin  knife-blade  crystals  which  range 
in  lenght  from  microscopic  dimensions  up  to  three-fourths  of  an  inch 
and  are  oriented  in  about  the  same  direction  as  the  feldspar  brushes, 
penetrating  or  lying  between  them. 

Under  the  microscope  the  brush-shaped  crystals  are  seen  to  be  made 
up  not  of  feldspar  alone  but  of  a graphic  intergrowth  of  quartz  and 
feldspar  of  microscopic  dimensions.  The  brushlike  form  represents, 
however,  the  form  of  the  feldspar  crystal.  Quartz  having  one  optical 
orientation  frequently  extends  from  one  feldspar  crystal  into  a neigh- 
boring one.  The  microscope  shows  also  that  the  feldspar  is  not  all 
of  one  variety.  That  forming  the  brush-shaped  crystals  is  largely 
microcline,  but  some  plagioclase,  mostly  in  aggregates  of  irregular 
grains  between  the  brush-shaped  crystals,  is  associated  with  it.  The 
plagioclase  is  albite  and  is  in  places  graphically  intergrown  with 
quartz.  Quartz  with  the  same  optical  orientation  in  many  instances 
continues  from  a crystal  of  microcline  into  a neighboring  one  of  albite. 


24  PEGMATITES  AND  ASSOCIATED  ROCKS  OF  MAINE. 

The  long  straight  blades  of  biotite  are  idiomorphic  with  respect  to  the 
quartz  and  feldspar  grains  and  their  intergrowths.  The  biotite 
blades  are  paralleled  in  many  specimens  by  an  abundance  of  micro- 
scopic blades  of  muscovite  alternating  with  thin  layers  of  quartz. 
Other  blades  of  muscovite  traverse  the  rock  in  the  same  manner  that 
biotite  does,  though  they  are  much  smaller. 

The  coarseness  of  the  graphic  intergrowth  of  quartz  and  feldspar 
described  above  varies  notably,  even  where  only  one  quartz  and  one 
feldspar  individual  are  involved.  There  does  not  appear,  however,  to 
be  any  important  difference  in  the  relative  proportions  of  the  minerals 
involved.  On  the  contrary,  it  is  notable  that  the  areas  of  graphic 
intergrowth,  whether  coarse  or  fine,  terminate  very  abruptly  against 
areas  of  pure  feldspar  that  are  crystallographically  continuous  with 
the  feldspar  of  the  intergrowth  (PL  VIII)  and  that  show  no  transi- 
tion through  intergrowths  characterized  by  progressively  smaller 
proportions  of  quartz.  The  quartz  and  feldspar  thus  appear  to  be 
intergrown  in  rather  definite  proportions  or  not  at  all.a 

Very  little  is  known  of  the  physical-chemical  conditions  that  pro- 
duce the  peculiar  types  of  crystallization  described  above.  The  mode 
of  occurrence  in  the  Alaskan  and  New  Mexican  examples  suggests, 
however,  that  the  brush-shaped  crystals  developed  rapidly  in  a 
border  portion  of  the  magma  where  the  temperature  gradient  was 


a Adolph  Knopf,  of  the  U.  S.  Geological  Survey,  in  a personal  communication  states  that  he  has  observed 
radiating  graphic  intergrowths  identical  with  those  of  the  Maine  specimens  in  rocks  from  the  Cape  Mountain 
region  near  Cape  Prince  of  Wales  in  Alaska.  The  specimen  brought  from  the  field  was  indistinguishable 
in  appearance  from  the  Maine  specimens  except  that  the  graphic  intergrowth  was  slightly  finer  grained. 
Its  mode  of  occurrence,  however,  was  wholly  different.  It  occurs  at  the  border  of  sills  of  microcline- 
orthoclase-biotite  granite  which  radiate  from  a central  granite  massif  at  their  contact  with  limestones.  The 
latter  have  been  metamorphosed  by  the  granite  with  the  development,  within  3 feet  of  the  contact,  of 
numerous  contact-metamorphic  minerals.  The  contact  zones  of  micrographic  granite  range  up  to  8 inches 
or  so  in  width,  though  the  individual  brush-shaped  crystals  are  not  over  4 inches  in  length.  In  a microscopic 
section  parallel  to  the  long  axis  of  one  of  the  “brushes”  and  about  parallel  to  the  c (001)  pinacoid  of  one  of 
the  feldspar  crystals,  the  cross  sections  of  the  quartz  bands  are  for  the  most  part  elongate  rod-shaped.  In 
some  of  these  the  long  axis  is  the  direction  of  fastest  light  transmission;  in  others  it  is  the  direction  of 
slowest.  Single  microcline  crystals  may  be  intergrown  with  several  quartz  crystals,  each  with  slightly 
different  orientation  and  slightly  different  trend  of  their  blades,  which  repeat  in  miniature  the  brushlike 
forms  assumed  by  the  microcline  crystals.  A feature  observed  in  both  the  Maine  and  Alaskan  specimens  is 
the  frequent  abrupt  termination  of  the  quartzes  along  planes  transverse  to  the  axes  of  the  brushes,  other  sets 
of  intergrown  quartzes  beginning  with  equal  abruptness  farther  on.  The  microcline  is  crystallographically 
continuous  across  these  hiatuses.  In  other  places  the  fine  graphic  intergrowths  are  succeeded  abruptly  along 
planes  at  right  angles  to  the  length  of  the  brushes  by  coarse  ones.  As  in  the  Maine  specimen,  grains  of 
albite,  usually  graphically  intergrown  with  quartz,  occur  between  some  of  the  quartz-microcline  “brushes,” 
and  between  others  occurs  a granular  aggregate  of  quartz,  microcline,  and  albite.  There  are  occasional 
short  blades  of  biotite. 

Bands  of  brush-shaped  intergrowths  of  feldspar  and  quartz,  similar  in  appearance  to  the  Maine  and 
Alaska  occurrences  but  of  microscopic  dimensions,  were  also  studied  in  a microscope  slide  in  the  collection 
of  the  United  States  Geological  Survey.  This  shows  the  contact  between  a coarse  quartz  diorite  and  an 
intrusive  aplite  dike  from  New  Mexico.  For  0.15  millimeter  from  the  diorite  contact  occurs  a granular 
aggregate  of  quartz  and  feldspar  so  fine  that  it  may  represent  a devitrified  glass;  the  next  zone,  0.60  milli- 
meter Li  average  width,  is  made  up  of  brush-shaped  intergrowths  of  feldspar  and  quartz  radiating  from 
the  finely  crystalline  zone  mentioned  above  into  the  main  mass  of  aplite. 

Frank  C.  Calkins,  of  the  United  States  Geological  Survey,  reports  in  a personal  communication  the 
occurrence  near  Anaconda,  Mont.,  of  borders  1J  inches  or  so  in  width  similar  to  the  Alaskan  and  Maine 
occurrences  in  general  appearance,  at  the  contact  between  diorite  and  an  intrusive  mass  of  biotite  granite. 
No  specimens  of  these  were  collected  for  study  but  presumably  they  are  similar  in  structure  to  those  here 
described. 


U.  S.  GEOLOGICAL  SURVEY 


BULLETIN  445  PLATE  VIII 


PHOTOMICROGRAPH  OF  GRAPHIC  GRANITE  FROM  TOPSHAM,  MAINE. 

Magnified  about  34  diameters.  Note  the  abrupt  termination  of  areas  of  graphic  intergrowth  against  areas 
of  pure  feldspar,  even  where  the  feldspar  is  crystallographically  continuous  from  one  to  the  other. 


TEXTURE. 


25 


steep.  In  general  the  brushes  are  elongate  in  the  direction  probably 
characterized  by  the  most  rapid  temperature  variation,  that  is,  at 
right  angles  to  the  bordering  wall.  It  is  possible  that  progressive 
differences  in  concentration  of  the  magmatic  solution  as  the  wall 
rock  was  approached  were  also  in  part  the  cause  of  the  faster  growth 
of  the  crystals  in  that  direction.  The  brush-shaped  crystals  noted 
in  Maine  unquestionably  represent  a phase  of  the  pegmatite  crystal- 
lization, evidently  one  of  its  later  stages. 

In  addition  to  the  graphic  intergrowths  of  feldspar  and  quartz  the 
quartz  in  many  of  the  Maine  pegmatites  assumes  branching  or 
arborescent  forms  in  the  feldspar. 

Intergrowths  of  minor  constituents. — Graphic  intergrowths  are  not 
confined  to  feldspar  and  quartz  but  even  in  the  same  pegmatite  mass 
may  often  be  found  between  several  of  the  less  abundant  constitu- 
ents. The  most  common  of  these  are  intergrowths  of  muscovite  and 
quartz  in  which  a single  crystal  of  muscovite  is  penetrated  both 
parallel  to  and  across  its  laminse  by  quartz.  The  quartz  in  some 
specimens  seems  to  be  one  crystal,  in  others,  several.  The  pattern 
produced  on  surfaces  parallel  to  the  muscovite  cleavage  resembles 
that  of  graphic  granite  but  is  somewhat  less  regular.  In  some  speci- 
mens these  intergrowths  are  fine-grained  in  their  centers  and  become 
progressively  coarser  outward,  terminating  occasionally  in  blade- 
shaped crystals  of  muscovite.  In  some  places  the  intergrowths  are 
brush  or  rosette-shaped,  and  in  others  the  graphic  intergrowths  form 
borders  about  sharply  bounded  hexagonal  crystals  of  muscovite,  the 
muscovite  of  the  intergrowth  being  crystallographically  continuous 
with  that  of  the  crystal  core. 

Intergrowths  of  quartz  and  garnet  are  also  common  atLd  in  certain 
directions  through  them  have  a more  or  less  graphic  pattern.  Some 
of  these  intergrowths  are  2 to  3 inches  across  and  they  commonly 
possess  well-defined  crystal  faces,  their  outer  portions  being  almost 
entirely  garnet.  When  broken  open,  however,  they  are  seen  to  be 
intergrowths  of  garnet  with  quartz,  the  rods  and  blades  of  -the  latter 
in  many  places  radiating  toward  the  crystal  faces.  Garnet  is  locally 
intergrown  with  the  quartz  of  the  quartz-muscovite  intergrowths. 

Intergrowths  of  quartz  and  black  tourmaline  are  also  common, 
the  tourmaline  usually  radiating  from  a core  composed  wholly  of 
tourmaline.  At  Mount  Mica  clusters  of  nearly  parallel  black  tour- 
maline crystals,  mostly  from  one-eighth  to  one-half  inch  in  diam- 
eter, embedded  in  a satiny  matrix  of  very  minute  muscovite  flakes 
are  occasionally  found.  The  tourmaline  rods  of  these  intergrowths 
commonly  emerge  from  the  end  of  a large  tourmaline  crystal. 

Intergrowths  occur  of  a character  less  regular  and  intimate  than 
those  already  described.  Microcline  feldspar  is  locally  intergrown 
to  some  extent  with  muscovite,  lying  between  the  mica  folia  or 


26 


PEGMATITES  AND  ASSOCIATED  ROCKS  OE  MAINE. 


cutting  across  them.  Many  small  garnets  with  well-developed 
crystal  forms  are  partly  or  wholly  inclosed  by  muscovite.  Lath- 
shaped crystals  of  biotite  bordered  by  muscovite  are  sometimes 
found,  the  cleavage  planes  of  the  two  micas  being  absolutely  coin- 
cident. Crystals  of  tourmaline  lying  in  somewhat  flattened  form 
between  the  plates  of  a mica  crystal  are  common,  and  some  small, 
colored  specimens  are  of  much  delicacy  and  beauty.  At  Black 
Mountain,  in  Rumford,  spodumene  was  observed  intimately  inter- 
grown  with  quartz. 

Mica. — In  many  of  the  pegmatite  bodies  muscovite  is  not  evenly 
distributed  throughout  the  mass  but  is  most  abundant  in  certain 
zones.  (See  PI.  IX,  A.)  These  zones  appear  to  be  distributed 
through  the  pegmatite  in  a totally  haphazard  manner,  bearing  no 
relation  to  the  general  form  of  the  pegmatite  mass  nor  to  the  position 
of  the  wall  rocks.  The  central  portions  of  these  muscovite  belts  for 
a width  of  a few  inches  consist  of  an  aggregate  of  heterogeneously 
arranged  muscovite  plates,  few  of  them  more  than  one-fourth  inch  in 
diameter.  (The  hammer  head  in  the  illustration,  PI.  IX,  A,  rests 
on  one  of  these  central  fine-grained  portions.)  They  are  commonly 
plane  or  only  gently  undulating  throughout  their  length  and,  being 
lines  of  weakness,  are  usually  marked  by  a fracture  plane.  From  this 
fine-grained  portion  spearhead-shaped  books  of  muscovite,  showing 
wedge  structure  (see  p.  139),  project  in  a direction  nearly  at  right 
angles  to  the  general  plane  of  the  mica  belt ; some  of  these  muscovite 
books  are  a foot  in  length.  This  peculiar  distribution  of  muscovite 
is  not  readily  explainable;  but  it  seems  to  represent  a muscovite 
crystallization  proceeding  not  from  a single  center,  but  from  a plane 
or  from  a large  number  of  centers  lying  in  nearly  the  same  plane.  In 
the  pegmatite  of  the  Black  Mountain  mica  mine  in  Rumford,  where 
the  mica  locally  constitutes  three-fourths  of  the  pegmatite  mass,  the 
elongate  mica  books  near  the  schist  wall  rock  tend  to  orient  themselves 
with  their  long  axes  perpendicular  to  the  contact.  In  a number  of 
quarries  muscovite  crystallization  about  a center  is  exemplified  by 
the  presence  of  nearly  equidimensional  aggregates,  some  of  them  5 
feet  across,  consisting  of  small  heterogeneously  arranged  plates  aver- 
aging about  one-fourth  inch  in  diameter.  From  their  peripheries 
these  muscovite  aggregates  send  off  spearhead-shaped  muscovite 
books  into  the  surrounding  pegmatite. 

Biotite  may  occur  in  isolated  lath-shaped  crystals  penetrating  the 
pegmatite  in  all  directions  or  in  radiating  aggregates  of  such  crystals. 

Gem-bearing  pegmatites. — Pegmatites  particularly  rich  in  gem  min- 
erals exhibit  peculiarities  of  structure  not  present  in  the  normal  rock. 
Lithium  minerals,  such  as  colored  tourmalines,  lepidolite,  spodu- 
mene, etc.,  and  the  soda  feldspar  clevelandite,  are  concentrated  in  a 
zone  which  usually  parallels  the  plane  of  greatest  dimension  of  the 


U.  S.  GEOLOGICAL  SURVEY 


BULLETIN  445  PLATE  IX 


A.  MUSCOVITE-RICH  ZONES  IN  PEGMATITE.  G.  D.  WILLES  FELDSPAR  QUARRY, 

TOPSHAM. 


B.  POCKET,  ABOUT  3 FEET  IN  DIAMETER,  IN  GEM-BEARING  LAYER  AT  MOUNT  MICA. 

OPENED  JUNE,  1904. 

The  giant  compound  tourmaline  crystal  shown  in  Plate  XIV  came  from  this  pocket;  also  another  similar  but 
smaller  compound  tourmaline  crystal;  two  large  simple  tourmaline  crystals,  one  of  which  is  shown  in 
Plate  XV;  about  $1,300  worth  of  red  and  pink  gem  tourmalines;  and  about  $300  worth  of  green  gem 
tourmalines.  In  all  the  pocket  yielded  about  75  pounds  of  tourmaline.  Photograph  by  Mr.  A.  A.  Norton, 
of  Portland,  Maine. 


ORIGIN. 


2 1 


commonly  lens-shaped  pegmatite  body.  Within  this  zone  pockets 
are  also  apt  to  be  particularly  abundant.  Pockets  are  found  in 
some  of  the  normal  pegmatites  also,  but  their  disposition  seems  to 
be  wholly  sporadic  and  most  of  them  are  barren  of  gem  minerals, 
though  some  contain  groups  of  fine  quartz  crystals  or  of  small  feld- 
spar crystals  on  their  walls. 

In  the  richly  gem-bearing  pegmatites  the  zone  of  sodium  and 
lithium  minerals  is  generally  separated  from  the  normal  pegmatite 
which  borders  it  by  a highly  garnetiferous  zone  from  an  inch  to 
several  inches  wide,  the  garnet  being  associated  with  a granular 
aggregate  of  quartz  and  feldspar.  A few  such  bands  are  paralleled 
by  a second  one  of  similar  character  1 or  2 inches  away.  These 
garnet  bands  are  frequently  of  practical  service  in  tracing  the  gem- 
bearing  zone.  The  pegmatite  outside  them  is  invariably  barren  of 
gem  minerals. 

As  explained  in  the  detailed  descriptions  of  Mount  Mica  and  other 
gem  localities,  the  gem  tourmalines  are  usually  found  in  pockets, 
having  developed  on  their  walls.  The  pockets,  though  confined 
mainly  to  the  zone  rich  in  soda  and  lithium  minerals,  may  be  wholly 
absent  from  considerable  portions  of  such  zones  and  are  distributed 
with  great  irregularity  through  the  remaining  portions.  The  char- 
acter and  distribution  of  pockets  is  best  illustrated  at  the  Mount 
Mica  tourmaline  mine.  Plate  XII  is  from  an  early  photograph  of  the 
workings  at  Mount  Mica,  taken  at  a time  when  only  the  outcropping 
portion  of  the  gem-bearing  zone  had  been  worked.  A stake  with 
card  attached  marks  the  position  of  each  pocket. 

Most  of  the  pockets  are  somewhat  spherical  in  form,  but  others 
are  oval  or  elongate  and  others  exceedingly  irregular.  Their  size 
ranges  from  a few  inches  across  to  a magnitude  such  as  is  shown 
in  Plate  XIII,  which  represents  the  largest  pocket  ever  found  at 
Mount  Mica. 

Minor  details  of  structure  of  the  gem-bearing  pegmatites  are  dis- 
cussed in  the  locality  descriptions  (p.  18). 

ORIGIN  OF  THE  MAINE  PEGMATITES. 

The  writer  does  not  purpose  in  this  report  to  discuss  the  volumi- 
nous literature  on  pegmatites  except  in  so  far  as  it  bears  closely  on 
those  of  the  region  under  discussion.  Previous  writings  and  theories 
have  been  well  summarized  by  George  H.  Williams  a and  especially  by 
Brogger.6 

RELATIONS  TO  GRANITES. 

The  geologic  relations  of  the  Maine  pegmatites,  as  already  pointed 
out  (pp.  13-15),  show  beyond  reasonable  doubt  that  they  are  geneti- 


a Williams,  G.  H.,  Fifteenth  Ann.  Rept.  U.  S.  Geol.  Survey,  1895,  pp.  675-684. 

b Brogger,  W.  C.,  Der  Syenitpegmatit-gange  der  sudnorwegischen  Augit  und  Nephelinsyenite:  Zeitsehr. 
f.  Kryst.,  vol.  16, 1890.  Sections  on  genesis  translated  in  Canadian  Rec.  Sci.,  vol.  6, 1894,  pp.  33-46,  61-71, 


28  PEGMATITES  AND  ASSOCIATED  ROCKS  OF  MAINE. 

cally  connected  in  a most  intimate  manner  with  the  granites.  Evi- 
dence of  this  is  found  in  mineralogical  similarity,  in  the  invariable 
presence  of  granite  in  all  areas  where  pegmatite  is  found,  and  in 
many  actually  observed  transitions  from  one  to  the  other.  (See 
fig.  2.) 

If  we  admit  a genetic  connection  between  the  pegmatites  and 
granites,  it  is  next  of  importance  to  inquire  what  evidence  is  afforded 
by  the  Maine  pegmatites  as  to  the  physical  and  chemical  conditions 
which  resulted  in  the  crystallization  from  related  magmas  of  rocks 
of  such  widely  varying  character. 

EXTERNAL  CONDITIONS. 

Differences  in  external  conditions  at  the  time  of  crystallization 
appear  inadequate  to  explain  the  observed  textural  differences. 
This  is  shown  by  the  close  association  of  the  two  types  of  rocks — an 
association  already  cited  as  evidence  of  their  genetic  relationships. 
The  field  relations  show  that  in  many  instances  the  external  condi- 
tions, such  as  the  nature  and  temperature  of  the  wall  rock,  the  depth 
at  which  solidification  took  place,  etc.,  were  similar  for  both  types 
of  rocks.  In  cases  such  as  that  shown  in  figure  2 the  general  exter- 
nal conditions  must  have  been  practically  identical.  A similar  con- 
clusion is  justified  in  numerous  other  instances  where  granite  and 
pegmatite  grade  into  each  other,  and  especially  where  pegmatite  forms 
segregation-like  masses  wholly  inclosed  in  granite.  Conversely,  the 
broad,  general  similarity  of  the  pegmatites  over  very  large  areas 
where  the  external  conditions  were  certainly  not  constant  also  indi- 
cates that  the  causes  of  their  peculiar  textures  were  in  the  main 
internal  rather  than  external.  It  seems  necessary  to  look,  there- 
fore, to  differences  inherent  in  the  magmas  themselves  for  an  expla- 
nation. 

DOMINANT  CONSTITUENTS. 

The  characters  shown  by  the  Maine  pegmatites  accord  with  the 
evidence  obtained  from  many  other  districts  in  indicating  (1)  that 
the  pegmatite  magmas  were  characterized  as  a general  rule  by  the 
presence  of  certain  components  in  amounts  larger  than  occur  in  nor- 
mal granite  magmas,  and  (2)  that  to  these  differences  in  composi- 
tion were  in  large  measure  due  the  differences  in  texture.  The  exact 
nature  of  such  differences  is,  however,  more  largely  a matter  of 
inference  than  of  direct  field  observation. 

In  the  great  mass  of  the  normal  pegmatite  it  is  exceedingly  diffi- 
cult, if  not  impracticable,  to  make  a satisfactory  estimate  of  the  rela- 
tive proportions  of  the  different  mineral  constituents.  So  far  as  can 
be  judged  without  measurements  the  proportions  are  of  the  same 


CONSTITUENTS. 


29 


general  order  as  in  the  normal  granites,  except  that  the  pegmatites 
are  probably  on  the  average  slightly  more  quartzose,  a conclusion 
that  seems  warranted  by  the  numerous  transitions  from  pegmatite 
masses  into  veins  composed  largely  or  wholly  of  quartz.  The  differ- 
ences in  the  proportions  of  the  principal  mineral  constituents  m the 
normal  granites  and  the  normal  pegmatites  seem,  however,  insuffi- 
cient to  account  for  the  great  differences  in  their  textures.  It 
appears  necessary  to  seek  the  cause  of  these  contrasts  in  differences 
in  the  proportions  of  minor  constituents  or  in  the  presence  in  the 
granite  or  pegmatite  magmas  of  constituents  which  have  since  escaped 
or  which,  through  occlusion,  are  not  now  visible  to  the  unaided 
eye  in  the  derived  rocks. 

MINOR  CONSTITUENTS. 

The  presence  in  many  pegmatites  of  unusual  minerals,  such  as 
fluorite  and  other  fluorine-bearing  minerals,  lithium  minerals,  boron 
and  phosphorus  minerals,  and  occasionally  rare  earth  minerals,  has 
led  certain  geologists®  to  attribute  to  some  of  these  substances  an 
important  role  in  the  production  of  pegmatite  textures.  It  can  not 
be  doubted  that  when  present  in  magmas  such  substances  have  some 
influence  upon  the  texture  of  the  resulting  rock.  It  has  not  been 
demonstrated,  however,  that  the  presence  of  these  unusual  constitu- 
ents is  essential  to  the  development  of  typical  pegmatitic  textures. 
In  the  opinion  of  the  writer  their  presence  is  probably  not  essential. 
The  pegmatites  which  earliest  attracted  the  attention  of  American 
mineralogists  and  geologists,  and  which  have  been  most  often  de- 
scribed in  the  literature,  were  naturally  those  in  which  unusual  min- 
erals were  present  in  especial  abundance  or  in  perfection  of  crystal 
form.  Such  pegmatites  constitute,  however,  only  an  exceedingly 
small  proportion  of  the  pegmatite  in  any  district  and  must  be  regarded 
as  unusual  rather  than  as  normal  types.  The  writer  is  familiar  with 
certain  deposits  showing  typical  pegmatitic  textures,  which  have 
been  worked  for  their  feldspar  for  years  with  the  discovery  of  few  if 
any  of  the  rarer  minerals.6  In  by  far  the  greater  number  of  the 
pegmatites  of  Maine  unusual  minerals  are  so  uncommon  as  ordi- 
narily to  escape  detection.  In  pegmatites  in  which  they  are  present 
their  paucity  or  abundance  seems  to  have  small  influence  on  the  tex- 
tures developed.  Those  inclined  to  attribute  large  influence  in  the 
development  of  pegmatitic  textures  to  the  presence  of  rare  constit- 
uents usually  contend  that  a more  careful  study  will  show  that  their 
scarcity  is  more  apparent  than  real.  Such  an  assumption  is  not  in 

t/  a Certain  French  geologists  in  particular  have  supported  this  view.  See  De  Lapparent,  Traite  de 
geologie,  4th  ed.,  1900,  p.  639;  De  Launay,  La  science  geologique,  1905,  pp.  557-558,  582-583. 

b The  Andrews  feldspar  quarry  in  Portland,  Conn.,  the  Mitchell  feldspar  quarry  in  Maryland,  and  the 
Goldings  feldspar  quarry  in  Georgetown,  Me.,  are  examples.  See  Bull.  U.  S.  Geol.  Survey  No.  420,pp.50, 
75,  and  this  report,  p.  105. 


30 


PEGMATITES  AND  ASSOCIATED  ROCKS  OF  MAINE. 


accord  with  the  field  observations  of  the  writer  in  Maine  and  other 
parts  of  New  England,  and  it  appears  to  be  unwarranted. 

GASEOUS  CONSTITUENTS. 

If  neither  the  dominant  nor  the  rare  minerals  of  the  pegmatites 
have  been  controlling  factors  in  the  development  of  typical  pegmatitic 
textures,  it  appears  necessary  to  seek  an  explanation  in  the  presence 
in  the  magmas  of  certain  constituents  which  have  subsequently 
escaped  or  at  least  are  not  readily  recognizable  in  the  resultant  rock. 
The  fact  that  large  crystals  can  not  be  obtained  at  atmospheric 
pressures  from  simple  dry  melts  of  the  commoner  rock-forming  min- 
erals suggests  at  once  that  the  crystallization  of  these  minerals  in 
nature  took  place  either  under  widely  different  physical  conditions 
(such  as  high  pressure)  or  in  the  presence  of  certain  substances  which 
are  scarce  or  absent  in  the  rocks  as  now  exposed.  It  has  already  been 
argued  from  field  evidence  (p.  28)  that  in  many  instances  differences 
in  pressure  or  other  external  conditions  at  the  time  of  crystalliza- 
tion can  not  reasonably  be  adduced  to  explain  the  textural  varia- 
tions observed.  In  such  cases  an  appeal  to  the  escaped  constituents 
of  the  magma  appears  unavoidable.  The  same  conclusion  appears 
necessary  when  the  extreme  viscosity  exhibited  (under  atmospheric 
pressures)  by  silica,  orthoclase,  and  albite  near  the  melting  tempera- 
tures is  considered.  The  various  forms  of  silica  that  have  been  arti- 
ficially produced  have  all  crystallized  from  a melt  so  viscous  as  to  be 
virtually  a glass.®  As  regards  orthoclase  the  viscosity  of  its  melt 
is  so  great  that  all  attempts  to  crystallize  the  mineral  from  it  have 
been  unsuccessful.  Since  increase  in  pressure  can  hardly  be  appealed 
to  as  increasing  molecular  mobility  b in  magmas,  it  seems  necessary 
again,  in  accounting  for  the  large  crystals  developed  in  the  pegmatites, 
to  postulate  the  presence  in  the  magma  of  some  substance  or  sub- 
stances not  now  recognizable  in  the  derived  rock.  That  the  presence 
of  volatile  constituents  in  a magma  does  influence  the  viscosity  is 
shown  by  the  fact  that  certain  obsidians  may  be  readily  melted  with 
evident  fluidity  and  the  escape  of  gases,  but  that  their  refusion  after 
such  gases  have  escaped  is  much  more  difficult.  Iddingsc  has  also 
shown  from  a microscopic  study  of  the  obsidian  of  Obsidian  Cliff, 
Yellowstone  National  Park,  that  where  there  was  more  dissolved 
gas  the  conditions  were  more  favorable  for  crystallization  than  in 
other  parts  of  the  magma. 

Among  those  constituents  of  magmas  which  might  escape,  leaving 
little  record  of  their  former  presence,  water  gas  and  hydrogen  are 

a Day,  D.  T.,  and  Shepherd,  E.  S.,  The  lime-silica  series  of  minerals:  Am.  Jour.  Sci.,  4th  ser.,  vol.  22, 
1906,  pp.  271-273.  Day,  D.  T.,  and  Allen,  E.  T.,  The  isomorphism  and  thermal  properties  of  the  feld- 
spars: Pubs.  Carnegie  Inst.,  No.  31,  1905,  pp.  28-29  and  45-55. 

• b Harker,  Alfred,  The  natural  history  of  igneous  rocks,  1909,  pp.  163-164. 

biddings,  J.  P.,  Seventh  Ann.  JEtept.  U.  S.  Geol.  Survey,  1888,  pp.  283-287.  Also  Igneous  rocks,  1909, 
p.  185. 


CONSTITUENTS. 


31 


probably  the  most  abundant,  as  is  plainly  indicated  by  analyses  of 
the  gases  still  remaining  in  igneous  rocks  a and  by  studies  of  the  gases 
emitted  from  volcanic  vents. h/ 

"''The  presence  of  water  gas  in  association  with  subordinate  amounts 
of  other  gases  and  of  certain  unusual  substances  (mineralizers)  has 
been  considered  by  many  observers  to  be  the  competent  and  effective 
cause  in  the  development  of  pegmatitic  textures.  With  this  opinion 
the  present  writer  is  in  general  accord,  though  the  persuasion  is  based 
more  largely  on  the  process  of  reasoning  already  outlined  than  on 
field  evidence  of  high-water  content  or  relatively  low  viscosity  in  peg- 
matite magmas.  The  field  evidence  gathered  in  the  study  of  the  Maine 
pegmatites  is  summarized  later  (p.  45),  but  must  be  looked  on  as 
merely  suggestive;  anything  like  a complete  solution  of  the  problem 
will  in  all  probability  wait  upon  synthetic  laboratory  experiments 
on  the  interaction  between  gases  and  rock-forming  silicates. 

The  small  weight  of  the  gaseous  and  liquid  constituents  of  most 
igneous  rocks  as  compared  with  the  total  weight  of  the  rock  might 
lead  one  to  question  their  competence  to  notably  affect  the  viscosity 
of  magmas  and  to  produce  large  textural  variations.  In  this  connec- 
tion it  may  not  be  out  of  place  to  call  attention  to  a possible  applica- 
tion of  Raoult’s  law,0  according  to  which  if  various  substances  are 
dissolved  in  equal  amounts  of  the  same  solvent  in  the  proportions  of 
their  molecular  weights  the  resulting  lowering  of  the  freezing  point 
of  the  solution  will  be  the  same  in  each  case.d  In  other  words,  the 
effect  produced  is  a function  of  the  number  of  molecules  concerned 
and  is  not  primarily  dependent  on  the  nature  of  the  substances 
introduced.  It  follows  that  a small  amount  by  weight  of  a substance 
of  low  molecular  weight  (such  as  H20,  molecular  weight  18)  will 
exert  the  same  depressing  influence  on  the  freezing  point  of  the  solu- 
tion as  a much  greater  weight  of  a substance  of  high  molecular  weight 
(such  as  Fe203,  molecular  weight  160);  and  that  given  equal  weights 
of  the  two  the  substance  of  lower  molecular  weight  will  exercise 
much  the  greater  influence.  This  law  has  been  found  to  apply 
strictly  only  to  very  dilute  solutions  where  there  is  no  chemical  action 
between  solvent  and  dissolved  substance.  It  has  been  applied  by 
Vogt6  to  rock  magmas,  but  the  wisdom  of  such  extension  to  cover 
widely  different  and  much  more  complex  physical  conditions  may 
well  be  questioned.  It  seems  not  unreasonable,  however,  to  attribute 
some  general  importance  to  this  principle  in  rock  magmas,  to  the 
extent  that  magmatic  constituents  of  low  molecular  weight  may  exert 

a Chamberlin,  R.  T.,  The  gases  in  rocks:  Pubs.  Carnegie  Inst.  No.  106, 1908.  This  includes  a summary  of 
earlier  investigations. 

b For  a review  of  the  literature  on  volcanic  gases,  see  Clarke,  F.  W.,  The  data  of  geochemistry:  Bull. 
U.  S.  Geol.  Survey  No.  330,  1908,  pp.  212-236. 

c Ostwald,  Wilhelm,  Outlines  of  general  chemistry,  1895,  pp.  13&-137. 

d Neglecting  electrolytic  dissociation,  which  is  probably  of  small  importance  in  rock  magmas. 

«Vogt,  J.  H.  L.,  Die  Silikatschmelzlosungen,  vol.  2,  1904,  pp.  128-135. 


32 


PEGMATITES  AND  ASSOCIATED  ROCKS  OF  MAINE. 


greater  influence  in  lowering  the  freezing  point,  decreasing  viscosity, 
and  affecting  textures,  than  do  constituents  of  high  molecular 
weight.  They  may  thus  attain  an  importance  which  appears  dis- 
proportionate to  the  small  part  by  weight  which  they  form  of  the 
whole  magma.  The  substances  (hydrogen,  water,  fluorine,  chlorine, 
and  boron)  commonly  believed  to  exert  the  greatest  influence  upon 
the  viscosity  of  magmas  and  the  textures  of  the  resulting  rocks  are 
all  substances  of  much  lower  molecular  weights  than  silica  and  the 
rock-making  silicates  and  oxides,  even  if  minimum  values  for  the 
latter  are  assumed.  The  hiatus  between  the  molecular  weights  of 
these  two  groups  of  substances  is  so  marked  as  to  justify  the  reten- 
tion of  the  term  11  mineralizers”  for  the  lighter  group,  in  case  the 
principle  outlined  above  is  eventually  shown  to  be  operative  to  an 
important  degree  in  magmas.  x 


VISCOSITY  AND  GAS  CONTENT. 

The  field  and  laboratory  data  on  the  pegmatites  of  Maine  that 
bear  on  the  viscosity  and  gaseous  content  of  the  pegmatite  magmas 
may  be  set  forth  as  follows.  As  the  pegmatite  magmas  crystallized 
at  some  distance  below  the  surface,  the  gases  which  they  contained 
must  either  have  made  their  escape  through  the  wall  rocks  or  else 
must  have  remained  in  cavities  or  occluded  within  the  solid  pegmatite 
mass.  The  escape  of  such  materials  through  the  wall  rocks  should 
presumably  leave  some  record  in  contact-metamorphic  effects. 
Their  retention  within  the  rock  should  presumably  be  recorded  in 
an  especial  abundance  of  miarolitic  cavities  and  fluid  or  gaseous 
inclusions.^  .A/  ^ > 

Miarolitic  cavities. — The  field  studies  of  the  writer  in  Maine  and 
other  parts  of  New  England  show  that  the  granites  are  almost 
wholly  devoid  of  miarolitic  cavities  of  any  kind.  An  isolated  cavity 
of  small  size  is  occasionally  found,  but  its  walls  are  usually  more  or 
or  less  pegmatitic  in  texture.  In  the  great  bulk  of  the  pegmatites  of 
Maine,  particularly  the  finer-grained  ones,  such  cavities  are  also 
exceedingly  rare.  In  the  coarser  pegmatites,  however,  they  are  a 
characteristic  feature,  though  usually  as  far  as  can  be  judged  con- 
stituting considerably  less  than  1 per  cent  of  the  total  volume  of  the 
pegmatite/  Within  the  very  narrow  gem-bearing  zones  of  certain 
pegmatites  miarolitic  cavities  may  form  a considerably  larger  per- 
centage of  the  total  volume,  ^uch  cavities  have  been  attributed  by 
various  writers  to  shrinkage  of  the  pegmatite  mass  in  crystallization. 
This  may  in  fact  play  some  part  in  their  formation,  but  that  they  are 
not  entirely  the  result  of  shrinkage,  but,  on  the  contrary,  were  filled 
or  partly  filled  with  some  material  which  has  since  disappeared,  is 
shown  by  the  presence  of  perfectly  developed  crystals  of  quartz, 
tourmaline,  and  other  minerals  projecting  inward  from  the  walls  of 


CONTACT-METAMORPHIC  EFFECTS. 


33 


the  cavities.  Some  filling  must  have  been  present  from  which  such 
crystals  derived  the  materials  for  their  growth.  It  is  probable, 
therefore,  that  immediately  after  the  crystallization  of  the  main  body 
of  pegmatite  the  miarolitic  cavities  were  completely  filled  with  a gase- 
ous solution,  which  may  later  have  liquified  and  has  since  disappeared. 
Water  carrying  numerous  other  substances  in  solution  probably 
formed  the  bulk  of  this  cavity  filling.  The  abundance  of  quartz 
crystals  on  the  walls  of  these  cavities  indicates  that  silica  was  one  of 
the  most  abundant  of  the  dissolved  substances./ 

If  the  crystallization  of  the  rock  with  pegmatitic  rather  than 
granitic  texture  is  due  to  the  presence  of  larger  amounts  of  gaseous 
constituents,  greater  size  or  abundance  of  microscopic  fluidal  or 
gaseous  cavities  might  reasonably  be  expected  in  the  pegmatite 
minerals  than  in  those  of  the  normal  granites.  With  this  idea  in 
mind  the  writer  attempted  a microscopic  measurement  of  these 
inclusions  in  pegmatites  and  associated  granites  from  Maine.  On 
account  of  the  uneven  distribution  of  the  inclusions  in  bands  travers- 
ing the  minerals  accurate  estimates  were  found  to  be  impracticable 
and  the  results  were  negative  or  inconclusive.  It  was  found,  more- 
over, that  some  of  the  bands  of  fluidal  cavities  in  the  quartz  of  peg- 
matite were  formed  later  than  shearing  movements  which  had  affected 
the  quartz./  (See  PL  VI.)  The  inclusions  in  the  pegmatite  were 
similar  in  character  to  those  in  the  normal  granites  of  the  State  and 
any  differences  in  their  size  and  abundance  in  the  two  types  of  rocks 
was  not  sufficient  to  be  noted  on  casual  inspection. 

^ Contact-metamorphic  effects. — If  the  pegmatite  magmas  are  charac- 
terized by  considerably  larger  proportions  of  gaseous  constituents 
than  are  present  in  the  granite  magmas  and  hence  by  notably  greater 
fluidity,  notable  differences  might  be  expected  in  the  contact-meta- 
morphic  effects  produced  by  the  two  types  of  rocks,  since  such  effects 
are  believed  to  be  produced  largely  by  gaseous  and  fluid  emanations 
from  the  cooling  igneous  masses.  Field  observations  in  Maine  fail  to 
show  that  contact-metamorphic  effects  due  to  the  intrusions  of  peg- 
matite are  notably  greater  than  those  produced  by  the  granites.  The 
effects  produced  by  both  are  usually  slight  and  in  many  instances 
almost  nil.  In  many  places  masses  both  of  pegmatite  and  granite 
cut  across  the  foliation  of  schists  without  any  distortion  of  the  latter, 
the  contacts  being  of  knife-edge  sharpness.  In  other  places,  however, 
pegmatite  has  produced  a notable  softening  of  the  bordering  rock, 
though  this  effect  is  usually  apparent  only  close  to  the  contact./ 

A striking  instance  of  this  effect  was  observed  about  2\  miles 
northeast  of  Paris  village,  where  a pegmatite  mass  2 to  3 feet  across 
and  several  smaller  masses  are  intrusive  in  schists  of  probable 
metamorphic-sedimentary  origin.  (See  PL  X,  A.)  ^Although  the 
63096°— Bull.  445—11 3 


34 


PEGMATITES  AND  ASSOCIATED  ROCKS  OF  MAINE. 


schist  folia  do  not  in  general  conform  to  the  outline  of  the  large 
pegmatite  mass,  as  they  would  if  any  considerable  amount  of  soften- 
ing had  occurred,  still  in  a zone  an  inch  or  two  wide  along  the  imme- 
diate contact  such  softening  has  taken  place  with  a deflection  of 
schist  folia  toward  parallelism  with  the  pegmatite  contact.  The 
bending  of  the  schist  folia  in  the  manner  shown  indicates  also  that 
the  pegmatite  when  intruded  behaved  to  a certain  extent  like  a solid 
body  capable  of  exerting  differential  thrust  on  the  inclosing  walls  of 
schist.  In  a body  behaving  essentially  like  a liquid,  pressure  would 
be  equ  alized  in  all  directions  and  it  is  difficult  to  see  how  such  bending 
of  folia  along  the  borders  of  the  mass  could  occur./ 

Another  instance  of  still  more  extensive  softening  of  the  schists 
bordering  pegmatite,  with  the  development  therein  of  minerals 
derived  from  the  pegmatite  magma/was  observed  at  Rumford  Falls 
(PI.  X,  B).  The  contact  is  very  irregular  and  the  schist  folia  near  the 
contact  curve  around  so  as  to  conform  rather  closely  to  the  outline 
of  the  pegmatite  mass.  Not  only  are  there  irregular  protuberances 
of  the  pegmatite  into  the  schist,  but  there  are  developed  in  the  schist 
next  to  the  contact  a number  of  masses,  mostly  composed  of  feldspar 
but  with  some  admixture  of  quartz,  which  in  the  plane  of  the  section 
are  not  connected  with  the  main  pegmatite  mass.  There  may,  of 
course,  have  been  some  connection  between  them  and  the  main  peg- 
matite body,  either  above  or  below  the  plane  of  the  present  surface 
of  exposure^  A feature  of  especial  interest  is  the  development  in 
some  of  these  masses  of  well-defined  crystal  faces,  as  is  clearly  shown 
in  Plate  X,  B , especially  in  the  mass  to  which  the  hammer  handle 
points.  " The  straight  faces  on  these  masses  are  parallel  to  the  cleavage 
directions  in  the  feldspar  and  there  can  be  no  doubt  that  they  are 
crystal  faces.  These  relations  plainly  indicate  a considerable  per- 
meation of  the  schist  by  the  pegmatite  magma  and  a sufficient  yield- 
ing on  the  part  of  the  schist  to  permit  the  development  of  very  perfect 
crystal  faces  in  the  feldspar.  This  may  have  been  accomplished 
through  absorption  or  by  metasomatic  replacement  of  the  schist,  but 
other  evidence  of  absorption  is  wholly  absent,  for  the  contacts  though 
very  irregular  are  very  sharp,  and  no  difference  is  noticeable  between 
the  pegmatite  next  the  contact  and  that  some  distance  away.  It 
seems  more  probable,  therefore,  that  the  phenomena  observed  indi- 
cate a yielding  of  the  schist  through  recrystallization  to  the  pressures 
of  various  kinds  exerted  by  the  pegmatite. 

Further  instances  of  the  softening  of  the  schists  as  a result  of  the 
intrusion  of  pegmatite  are  exemplified  by  numerous  occurrences  of 
the  type  illustrated  diagrammatically  in  figure  1 (p.  11),  where  the 
schist  laminae  show  a thickening  opposite  the  nodes  of  the  pegmatite 
dike  or  sill  and  become  thinner  opposite  the  bulges. 


U.  S.  GEOLOGICAL  SURVEY 


BULLETIN  445  PLATE  X 


A.  DEFLECTION  OF  SCHIST  FOLIA  ALONG  THE  IMMEDIATE  CONTACT  WITH  A PEGMATITE 

DIKE. 

Two  and  one-half  miles  northeast  of  Paris  village,  Oxford  County. 


B.  DEVELOPMENT  OF  FELDSPAR  CRYSTALS  IN  SCHIST  NEAR  PEGMATITE,  RUMFORD  FALLS. 


FORMS  OF  THE  INTRUSIVES. 


35 


Such  softening  effects  as  those  cited  are  confined,  however,  to  the 
immediate  vicinity  of  the  pegmatite,  usually  to  a zone  a few  inches 
in  width,  and  are  the  exception  rather  than  the  rule,  most  pegmatite 
contacts  being  exceedingly  sharp  and  free  from  all  evidence  of  soften- 
ing. Absorption  (except  in  a few  doubtful  instances)  appears  to  be 
wholly  absent,  the  contacts  even  in  the  places  where  softening  is  shown 
being  sharp,  and  the  pegmatite  next  the  contact  showing  no  difference 
in  composition  from  that  at  some  distance  away.  Where  schist  frag- 
ments are  inclosed  in  the  pegmatite  their  sharp  outlines  are  preserved. 
Contact-metamorphic  effects  of  the  pegmatite  on  schists  are  particu- 
larly noticeable  at  Black  Mountain  in  Rumford.  (See  p.  96.) 

Forms  of  the  intrusives. — If  the  physical  conditions  of  the  pegmatite 
and  granite  magmas  were  notably  different  at  the  time  of  their  intru- 
sion, it  would  be  natural  to  expect  some  differences  in  the  forms 
assumed  by  the  granite  and  pegmatite  masses.  Though  in  many 
cases  those  forms  are  similar,  there  is  in  general  a tendency  for  the 
smaller  pegmatite  intrusions  in  the  foliates  to  assume  the  form  of  a 
succession  of  lenses  (fig.  1,  p.  11)  and  for  the  granite  intrusions  of 
similar  size  to  be  more  nearly  parallel  walled.  This  contrast  is  par- 
ticularly noticeable  in  the  Boothbay  Harbor  region  and  near  Rumford 
Falls  and  is  probably  expressive  of  slightly  greater  rigidity  in  the 
granite  than  in  the  pegmatite  magma  and  also  of  greater  softening 
of  the  inclosing  schist  by  the  pegmatite  than  by  the  granite  magmas. 
The  great  size  of  certain  pegmatite  masses,  such  as  Streaked  Mountain 
in  Hebron,  is,  on  the  other  hand,  suggestive  of  degrees' of  viscosity  in 
some  pegmatite  magmas  not  widely  different  from  those  prevailing  in 
normal  granite  magmas.  The  crest  of  Streaked  Mountain  was  exam- 
ined for  more  than  half  a mile  of  its  length  and  the  width  of  outcrop 
examined  across  the  trend  of  the  ridge  for  about  half  a mile.  The 
whole  area  traversed  and  the  remainder  of  the  mountain  as  far  as  it 
could  be  seen  was  underlain  almost  exclusively  by  coarse  pegmatite, 
the  mountain  being  a “boss”  of  this  material.  The  pegmatite  is  of 
the  usual  granitic  type  and  exhibits  no  more  than  the  usual  amount 
of  variation  in  texture  and  composition  from  point  to  point.  It  is 
difficult  to  conceive  of  a mass  of  this  size  and  general  uniformity  crys- 
tallizing under  anything  like  vein  conditions.  With  very  high  gaseous 
content  and  correspondingly  high  mobility  it  would  be  natural  to 
expect  more  differentiation  both  in  texture  and  composition.  It 
seems  probable  that  the  viscosity  of  such  a pegmatite  magma  was 
not  so  much  below  that  of  a granite  mass  intruded  under  similar  con- 
ditions as  has  been  commonly  supposed. 

Fragments  of  the  wall  rock  are  very  frequently  found  inclosed  by 
the  border  portions  of  the  granite  masses  of  Maine.  The  phenome- 
non is  much  less  common  in  the  case  of  the  pegmatites  but  was 


36 


PEGMATITES  AND  ASSOCIATED  ROCKS  OF  MAINE. 


nevertheless  observed  at  several  localities.  On  the  highest  portion 
of  Streaked  Mountain  a number  of  patches  of  schist  a few  square 
yards  in  area  were  seen  apparently  entirely  inclosed  by  pegmatite. 
Small  schist  fragments  are  also  inclosed  by  pegmatite  in  the  Booth- 
bay  Harbor  region.  W.  H.  Emmons,  of  the  United  States  Geological 
Survey,  who  visited  Mount  Mica  a year  later  than  the  writer,  when 
the  excavation  had  proceeded  farther,  observed,  a few  feet  below  the 
schist  hanging  wall,  schist  fragments  which  appeared  to  be  wholly 
inclosed  in  the  pegfffatite.  The  schistosity  of  these  fragments  made 
large  angles  with  the  schistosity  of  the  walls  from  which  they  had 
evidently  been  dislodged.  The  pegmatite  shows  no  bending  of  the 
minerals  nor  other  changes  in  character  near  the  fragments.  In  the 
instances  cited  the  schist  fragments  appear  to  have  been  caught  up 
while  the  pegmatite  mass  was  still  partly  or  wholly  fluid,  and  the 
density  of  the  magma  was  sufficient,  at  least  in  the  Mount  Mica 
example,  to  float  the  fragments. 

TEMPERATURES  OF  PEGMATITE  CRYSTALLIZATION. 

Experiments  of  Wright  and  Larsen. — Some  evidence  in  regard  to 
the  temperatures  of  the  pegmatites  at  the  time  they  crystallized  has 
been  obtained  from  studies  of  quartz  by  Wright  and  Larsen,  some  of 
the  specimens  being  collected  by  the  writer  from  the  pegmatites  of 
Maine  and  other  parts  of  New  England.  To  quote  from  their  paper — a 

For  * * * geologic  thermometric  purposes,  quartz  has  been  found  by  experi- 
ence to  be  well  adapted.  It  is  plentiful  in  nature  and  occurs  in  many  different 
kinds  of  rocks.  Si02  in  the  form  of-tridymite  melts  at  about  1,625°  (centigrade); 
between  that  temperature  and  about  800°  tridymite  is  the  stable  phase;  below  about 
800°  quartz  is  the  stable  phase.  From  evidence  thus  far  gathered  it  is  probable  that 
pressure  has  but  slight  effect  on  raising  or  lowering  such  an  inversion  point,  and 
that,  therefore,  whenever  quartz  appears  in  nature,  it  was  formed  at  a temperature 
below  800°. 

The  studies  of  Wright  and  Larsen  and  of  earlier  observers  have 
shown  that  at  about  575°  C.  there  is  a sudden  change  from  one  form  of 
crystal  symmetry  to  another.  Quartz  developed  below  575°  crystal- 
lizes in  what  has  been  called  the  a form  (the  trapezohedral-tetarto- 
liedral  division  of  the  hexagonal  system)  and  quartz  developed  above 
575°  appears  to  crystallize  in  the  /?  form  (the  trapezoliedral-hemihe- 
dral  division  of  the  same  system). 

Quartz  itself  undergoes  a reversible  change  at  about  575°.  * * * Practically 
the  only  crystallographic  change  which  takes  place  on  the  inversion  is  a molecular 
rearrangement,  such  that  the  common  divalent  axes  of  the  high  temperature  (3  form 
become  polar  in  the  a form,  and  this  fact  involves  certain  consequences  which  can 
be  used  to  distinguish  quartz  which  has  been  formed  above  575°  from  quartz  which 
has  never  reached  that  temperature.  At  ordinary  temperatures  all  quartz  is  ct  quartz, 
but  if  at  any  time  in  its  history  a particular  piece  of  quartz  has  passed  the  inversion 

a Wright,  F.  E.,  and  Larsen,  E.  S.,  Quartz  as  a geologic  thermometer:  Am.  Jour.  Sci.,  4th  ser.,  vol.  28, 
1909,  p.  423. 


TEMPERATURES  OF  PEGMATITE  CRYSTALLIZATION. 


37 


point  and  been  heated  above  575°,  it  bears  ever  afterwards  marks  potentially  j^resent 
which  on  proper  treatment  can  be  made  to  appear  Just  as  an  exposed  photographic 
plate  can  be  distinguished  at  once  from  an  unexposed  plate  on  immersion  in  a proper 
developer,  although  before  development  both  plates  may  be  identical  in  appear- 
ance.a 

In  addition  to  the  change  in  crystal  form  at  575°,  the  quartz 
exhibits  changes  in  its  coefficients  of  expansion,  in  circular  polariza- 
tion, and  in  birefringence. 

Briefly  stated,  the  four  criteria  which  can  be  used  to  distinguish,  at  ordinary 
temperatures,  quartz  which  was  formed  above  575°  froi^quartz  which  has  never 
been  heated  to  that  temperature,  are:  (1)  Crystal  form,  if  crystals  be  available,  the 
presence  of  trigonal  trapezohedrons  and  other  evidence  of  tetartohedrism,  irregular 
development  of  the  rhombs  and  the  like,  being  indicative  of  the  <?'form.  (2)  Char- 
acter of  twinning,  as  shown  by  etch  figures  on  the  basal  pinacoid.  In  the  a form, 
which  crystallized  from  solutions  at  comparatively  low  temperatures,  the  twinning 
is  usually  regular  and  sharply  marked,  while  in  quartz  plates  originally  of  the  /? 
form  and  now  a by  virtue  of  inversion  in  the  solid  state,  the  lines  are  usually  irregu- 
lar, and  the  twinning  patches  are  small  and  bear  no  relation  to  the  outer  form  of  the 
crystal.  (3)  Intergrowths  of  right  and  left  handed  quartzes  are  more  frequent  and 
more  regular  in  boundary  lines  in  the  a than  in  the  /?  form.  (4)  Plates  of  originally 
/?  quartz  but  now  <r  quartz  by  inversion  show  the  effect  of  the  inversion  by  the  shat- 
tering, which  should  be  most  evident  on  large  plates.  Into  all  these  criteria  an  ele- 
ment of  probability  enters,  and  in  testing  quartz  plates,  with  this  end  in  view,  a 
number  of  plates  should  be  examined  to  strengthen  the  validity  of  the  inferences 
drawn.  & 

The  bearing  of  the  experiments  on  the  temperatures  of  crystalliza- 
tion of  granites  anti  pegmatites  has  been  briefly  discussed  by  Wright 
and  Larsen,  but  the  writer  desires  to  amplify  the  discussion  by  a 
more  detailed  description  of  its  relation  to  those  specimens  with 
which  he  is  personally  familiar. 

No  granites  from  Maine  were  tested  by  Wright  and  Larsen,  but 
thirteen  specimens  of  granites,  granite  gneisses,  and  porphyries 
which  were  tested  from  other  regions  show  as  a rule  the  characters 
of  /?  or  high-temperature  quartz,  thus  placing  their  temperature  of 
final  solidification  above  575°  C. 

Two  specimens  of  rose  quartz  from  Maine  (Nos.  13  and  14,  Wright 
and  Larsen),  one  of  them  from  Paris,  Oxford  County,  now  in  the 
collection  of  the  United  States  National  Museum,  were  examined  by 
Wright  and  Larsen  and  found  to  show  the  characters  of  a or  low- 
temperature  quartz.  The  specimens  have  the  appearance  of  typical 
pegmatite  quartz;  and  in  Maine  rose  quartz,  so  far  as  known,  occurs 
only  as  a pegmatite  constituent. 

A specimen  of  rose  quartz  (No.  12,  W.  and  L.)  collected  by  the 
writer  from  the  feldspar  and  quartz  quarry  of  P.  H.  Kinkie’s  Sons 
at  Bedford,  N.  Y.,  also  showed  the  characteristics  of  a or  low- 

a Wright,  F.  E.,  and  Larsen,  E.  S.,  Quartz  as  a geologic  thermometer:  Am.  Jour.  Sei.,  4th  ser.,  vol.  28, 
pp.  423,  425. 
b Idem,  p.  438. 


38 


PEGMATITES  AND  ASSOCIATED  EOCKS  OF  MAINE. 


temperature  quartz.  This  pegmatite  has  been  described  by  the 
writer  in  another  report  a and  is  similar  in  most  of  its  character- 
istics to  the  coarser  Maine  deposits.  The  quartz  of  this  quarry  is 
mostly  white  but  is  rose  colored  in  places.  It  is  associated  with 
the  feldspar  in  a wholly  irregular  manner  and  forms  large  masses  in 
one  pit,  being  the  principal  rock  on  two  of  the  walls.  These  quartz 
masses  at  their  borders  are  in  intimate  interpenetration  with  the 
feldspar  and  may  even  grade  into  the  quartz  of  graphic  granite.' 
There  is  not  the  slightest  doubt  that  they  form  an  integral  part  of 
the  pegmatite  mass, ’Though  very  likely  the}7  were  the  latest  portion 
to  crystallize. 

Another  specimen  of  quartz,  collected  by  the  writer  from  the  peg- 
matite at  an  old  feldspar  quarry  on  the  northwest  side  of  Mount 
Ararat  in  Topsham,  showed  a quartz  crystal  about  1J  inches  across 
projecting  with  perfectly  developed  pyramid  faces  into  a crystal  of 
pink  microcline.  The  crystal  faces  of  the  quartz  were  only  shown 
when  the  feldspar  was  broken  away.  The  two  minerals  formed 
intimate  parts  of  a large  mass  of  coarse  pegmatite  and  plainly  crystal- 
lized contemporaneously.  The  tests  on  this  quartz  (No.  20,  W.  and 
L.)  indicate  that  it  crystallized  below  575°. 

Another  test  (No.  18,  W.  and  L.)  was  made  upon  quartz  collected 
from  the  Berry  feldspar  quarry  in  Poland,  Me.  The  deposit  is  a 
gem-bearing  pegmatite  and  the  quartz  tested  was  irregularly  inter- 
grown  with  rounded  lepidolite  and  bladed  al'bite  of  the  clevelandite 
variety.  It  occurred  in  the  solid  pegmatite  but  near  miarolitic  cav- 
ities. The  tests,  though  not  wholly  conclusive,  show  that  it  probably 
belongs  to  the  low-temperature  variety. 

Crystals  of  transparent  smoky  quartz  (No.  15,  W.  and  L.)  devel- 
oped on  the  walls  of  pockets  in  the  pegmatite  at  the  same  quarry 
exhibited  low-temperature  characters.  Similar  results  (No.  19,  W. 

- and  L.)  were  obtained  for  a compound  quartz  crystal  developed  in 
one  of  the  pockets  at  the  G.  D.  Willes  feldspar  quarry  in  Topsham. 
At  its  proximate  end  this  crystal  mass  was  intergrown  with  the  feld- 
spar of  the  wall  of  the  pocket.  It  was  plainly  a pegmatite  crys- 
tallization, though  a late  one. 

A specimen  (No.  16,  W.  and  L.),  taken  by  the  writer  from  a large 
mass  of  white  quartz  several  feet  across  in  the  pegmatite  at  the 
Fisher  feldspar  quarry  in  Topsham,  also  showed  the  characters  of 
the  a or  low-temperature  variety.  These  quartz  areas  form  an 
intimate  part  of  the  pegmatite  mass,  interlocking  at  their  borders 
with  crystals  of  the  other  constituents  and  in  places  grading  without 
break  into  the  quartz  of  coarse  graphic  granite. 

In  contrast  to  the  above  tests  on  specimens  of  quartz  from  the 
large  quartz  masses  in  the  pegmatites  and  from  the  quartz  in  or  near 

a Bastin,  E.  S.,  Feldspar  and  quartz  deposits  of  southeastern  New  York:  Bull.  U.  S.  Geol.  Survey 
No.  315,  1907,  pp.  395-398. 


EUTECTICS  IN  PEGMATITES. 


39 


the  cavities,  tests  of  smaller  masses  of  quartz  in’  finer-grained  peg- 
matite or  intergrown  with  feldspar  in  graphic  granite  show  that  in 
these  crystallization  took  place  above  the  inversion  point  of  575°  C. 
Quartz,  for  example,  from  a pegmatite  dike  1 to  4 feet  in  width, 
cutting  fine-grained  biotite  granite  in  a railroad  cut  near  Rumford 
Falls  (No.  22,  W.  and  L.),  proved  to  be  of  the  /?  or  high-temperature 
variety.  The  rock,  in  addition  to  quartz,  contained  microcline  and 
biotite,  few  of  the  feldspars  exceeding  2 inches  in  diameter.  This 
dike  in  texture  and  coarseness  is  typical  of  very  many  of  the  smaller 
pegmatite  bodies  of  the  State.  Similar  results  were  obtained  with 
quartz  (No.  25,  W.  and  L.)  from  the  coarse  graphic  granite  of  Fisher's 
feldspar  quarry  in  Topsham  (see  PL  XVIII,  and  an  analysis,  p.  124). 
At  this  quarry  much  of  the  feldspar  of  the  graphic  granite  is  crystal- 
lograpliically  continuous  with  large  masses  of  pure  feldspar,  and 
much  of  the  quartz  of  the  intergrowths  may  be  traced  into  the 
large  pure  areas.  Graphic  granite  of  similar  composition  and  coarse- 
ness (No.  23,  W.  and  L.)  collected  by  the  writer  from  the  Andrews 
feldspar  quarry  in  Portland,  Conn.,  also  showed  high-temperature 
characters.  Concordant  results  were  obtained  on  quartz  of  graphic 
granite  from  the  Urals  in  Russia. 

Application  to  Maine  pegmatites. — The  results  of  these  several 
tests  are  consistent  among  themselves  and  in  accord  with  the  order 
of  crystallization  of  various  portions  of  the  pegmatite  as  established 
by  field  evidence.  Though  it  is  not  safe  to  draw  sweeping  conclu- 
sions from  the  rather  small  number  of  tests  they  are  nevertheless 
very  suggestive  and  render  it  highly  probable  that,  although  many  of 
the  finer-grained  pegmatite  masses  and  most  of  the  graphic  inter- 
growths of  the  coarser  pegmatites  crystallized  at  temperatures  above 
575°  C.,  the  coarser  and  more  siliceous  portions — the  portions  char- 
acterized by  the  cavities  and  hence  presumably  richer  in  gaseous  or 
fluid  constituents — crystallized  at  temperatures  below  575°.  The 
portions  characterized  by  high  and  by  low  temperature  quartz  are 
commonly  so  intimately  associated  in  the  same  pegmatite  mass  that 
it  seems  unreasonable  to  assume  great  differences  in  the  temperature 
of  crystallization  of  different  portions.  It  is  probable,  therefore, 
that  the  whole  mass  of  many  of  the  coarser  pegmatites  crystallized 
not  far  from  the  inversion  point  of  quartz;  that  is,  not  far  from 
575°  C. 

EUTECTICS  IN  PEGMATITES. 

Largely  as  a result  of  the  extensive  studies  of  Vogt,a  many  geolo- 
gists5 have  been  led  to  attribute  to  eutectics  an  important  part  in 
rock  formation.  One  of  the  phenomena0  that  most  obviously  sug- 


o Vogt,  J.  H.  L.,  Die  Silikatschmelzlosungen,  vol.  2,  1903,  pp.  117-135. 
b Harker,  Alfred,  The  natural  history  of  igneous  rocks,  pp.  262-266,  270-272. 
c Teall,  J.  J.  H.,  British  petrography,  1888,  pp.  401-402. 


40 


PEGMATITES  AND  ASSOCIATED  DOCKS  OF  MAINE. 


Art 


gested  such  a relation  was  the  graphic  structure  exhibited  by  many 
pegmatites,  which  closely  resembled  patterns  formed  by  eutectic 
mixtures  in  alloys.  Vogt a calculated  the  ratio  between  quartz 
and  feldspar  in  a number  of  analyses  of  graphic  intergrowths  of 
quartz  with  microcline,  the  latter  mineral  being  also  perthitically 
intergrown  with  various  amounts  of  soda  plagioclase.  The  ratios 
were  constant  enough  to  lead  Yogt  to  conclude  that  the  graphic 
granites  represented  eutectic  mixtures.  Slight  disparities  between 
analyses  he  attributed  to  slight  variations  in  the  compositions  of 
the  feldspars  and  to  variations  in  the  pressures  under  which  the 
granites  had  crystallized.  In  many  specimens,  especially  in  micro- 
scopic varieties,  the 
graphic  intergrowths 
are  considered  to  be 
the  end  products  of 
crystallization. 

In  1905  H.  E. 
Johansson,6  working 
mainly  with  Vogt’s 
analyses,  computed 
the  molecular  pro- 
portjons  of  the 
quartz  and  feldspars 
present  and  con- 
cluded that  these 
bore  very  simple 
numerical  relations 

Figure  5.— Diagram  showing  composition  of  graphic  granite.  £q  each  other  In 

graphic  granites  with  dominant  orthoclase  the  molecular  ratio  of 
feldspar  to  quartz  was  about  2:3.  In  an  oligoclase  graphic  granite 
the  proportion  was  about  1:2,  and  in  an  albite-quartz  micropeg- 
matite it  was  about  1:3. 

Later  Bygdenc  made  a considerable  number  of  other  analyses 
of  graphic  granites  with  the  special  purpose  of  determining  to  what 
extent  the  quartz-feldspar  ratio  is  dependent  on  the  composition  of 
the  feldspar.  He  concluded  that  the  ratio  between  quartz  and 
feldspar  bore  no  regular  relationship  to  the  composition  of  the  feld- 
spar. He  believed  that  in  most  graphic  granites  definite  ratios  did 
exist  between  the  proportions  of  feldspar  and  quartz,  but  that  these 
ratios  were  not  always  so  simple  as  Vogt  and  Johansson  had  supposed. 

To  supplement  the  small  number  of  available  trustworthy  analy- 
ses the  writer  collected  specimens  of  graphic  granite  from  the  Fisher 

a Op.  cit.,  pp.  120-121. 

b Geologiska  foreningens  forhandlingar,  Stockholm,  vol.  27,  1905,  p.  119. 

cBygden,  A.,  tiber  das  quantitative  Verhaltnis  zwischen  Feldspat  und  Quartz  in  Schrift-graniten: 
Bull.  Geol.  Inst.  Univ.  Upsala,  vol.  7,  1904,  pp.  1-18. 


EUTECTICS  IN  PEGMATITES. 


41 


feldspar  quarry  in  Topsham,  Me.,  and  from  Kinkle’s  feldspar  quarry 
in  Bedford,  N.  Y.  These  were  analyzed  by  George  Steiger  in  the 
laboratory  of  the  United  States  Geological  Survey.  (See  p.  124.) 
In  order  that  the  material  analyzed  should  represent  closely  the 
true  composition,  about  10-pound  samples  of  the  Maine  granites 
were  taken.  These  were  pulverized,  carefully  mixed,  and  quar- 
tered down  to  convenient  size  for  analysis.  The  New  York  speci- 
men was  a cleavage  piece  about  1 by  2 by  3 inches  in  size. 

The  ratio  of  quartz  to  feldspar  in  the  analyses  published  by  Vogt 
and  Bygden  and  in  the  author’s  analyses  are  given  in  the  table 
below.  In  figure  5 the  compositions  of  the  feldspars  are  plotted 
on  triangular  projection.  The  numbers  in  the  diagram  correspond 
to  those  in  the  table. 


Composition  of  graphic  granites . 


No. 

Locality. 

Feld- 
spar. a 

Quartz,  a 

Molecular  percentages 
of  feldspar  compo- 
nents. 

Reference. 

Ortho- 

clase. 

Albite. 

Anor- 

thite. 

1 

2 

3 

4 

5 

6 
7-8 

9 

10 

11 

A 

B 

C 

D 

Skarpo 

Hittero 

Voie,  Arendal 

Elfkarled 

Topsham,  Me 

do 

Hittero 

Reade 

Arendal 

Bedford,  N.  Y 

Rodo 

Evje.  

Ytterby 

Beef  Island 

Per  cent. 

70.5 
66.0 

74.7 

79.2 
72.9 

73.7 

75.3 

72.7 

76.5 

76.8 

56.0 

68.3 

62.1 
81.7 

Per  cent. 

29.5 

34.0 

25.3 
20.8 

27.1 

26.3 

24.7 

27.3 

23.5 

23.2 
39.0 

31.7 
37.9 

18.3 

82.5 

77.6 

73.8 

74.8 

| 74.4 

69.1 

66.1 

63.9 

61.7 

9.6 
12.4 

4.3 

4.6 

15.1 
21.6 

24.0 

24.5 

25.6 

28.5 

28.2 

33.7 

37.0 

85.4 

76.0 

74.5 

68.0 

2.4 

.8 

2.2 

.7 

None. 

2.4 

5.7 

2.4 

1.3 

5.0 

11.6 

21.2 

27.4 

Bygden  No.  7. 

Bygden  No.  8. 

Vogt  No.  1. 

Bygden  No.  6. 

See  p.  112. 

Vogt  Nos.  2 and  3. 

Vogt  No.  4. 

Vogt  No.  5. 

See  p.  112. 

Bygden  No.  9 (Ilolmquist). 
Vogt  No.  6. 

Bygden  No.  11. 

Bygden  No.  12. 

a Calculated  from  the  analyses. 


From  the  table  and  diagram  it  is  at  once  evident  that  even  among 
those  graphic  granites  whose  feldspars  are  almost  identical  in  com- 
position (such  as  Nos.  2 to  6)  there  are  quite  considerable  variations 
in  the  quartz-feldspar  ratio.  In  analyses  Nos.  1,  2,  3,  7,  8,  10,  and 
11  (particularly  in  Nos.  1,  3,  7,  8,  and  10)  the  percentage  of  anorthite 
is  small  and  nearly  constant,  the  only  important  variation  being  in 
the  ratio  between  orthoclase  and  albite.  No  regular  or  consistent 
relationship  is  recognizable,  however,  between  this  ratio  and  the 
ratio  between  quartz  and  feldspar.  The  grouping  of  Nos.  1 to  11 
near  the  lower  line  of  the  diagram  signifies  merely  that  the  feldspar 
associated  with  the  orthoclase  (or  microcline)  in  graphic  granites 
as  in  normal  granites®  is  usually  albite  or  oligoclase. 

Both  analyses  and  microscopic  studies  show  that  most  graphic 
granites  are  mixtures  of  three  minerals — quartz,  orthoclase  or 


a Clarke,  F.  W.,  The  data  of  geochemistry:  Bull.  U.  S.  Geol.  Survey  No.  330,  1908,  p.  369. 


42  PEGMATITES  AND  ASSOCIATED  HOCKS  OF  MAINE. 

microcline,  and  a member  of  the  isomorphous  series  of  plagioclase 
feldspars.  It  should  be  pointed  out,  moreover,  that  if  water  or 
other  gases  were  present,  as  it  is  almost  certain  they  were,  they 
formed  additional  components  whose  amount  the  analyses  do  not 
reveal,  but  whose  influence  on  the  proportions  of  the  other  con- 
stituents may  have  been  great.  If  graphic  granites  crystallized 
from  magmas  of  eutectic  proportions  these  were  therefore  eutectics 
of  at  least  four  components.  The  series  of  analyses  (p.  41),  though 
suggesting  that  the  proportions  between  the  constituents  of  graphic 
granites  are  controlled  by  some  laws,  can  hardly  be  regarded  as 
proving  their  eutectic  origin.  The  theoretical  value  of  such  analy- 
ses in  elucidating  the  laws  governing  rock  solutions  is  impaired  by 
the  fact  that  they  take  no  account  of  the  gaseous  components  of 
the  magmas. 

Vogt  a states  that  many  graphic  intergrowths,  especially  when 
developed  on  a microscopic  scale,  represent  the  last  portions  of 
the  magma  to  crystallize.  This  fact  he  cites  as  in  harmony  with 
the  conception  that  they  represent  eutectic  residues.  Although  this 
may  be  the  true  relation  in  some  cases,  in  others  the  graphic  granite 
was  unquestionably  not  the  last  crystallization  from  the  magma. 
In  the  Fisher  feldspar  quarry  in  Topsham,  for  example,  where 
large  masses  of  graphic  granite  pass  gradually  and  irregularly  into 
large  areas  of  pure  quartz  and  feldspar,  the  tests  of  Wright  and 
Larsen  (see  p.  39)  have  shown  that  the  quartz  of  the  graphic  inter- 
growths crystallized  above  575°  C.,  whereas  the  quartz  of  the  large 
pure  areas  crystallized  below  575°.  The  latter  was  therefore  the 
later  crystallization.  Almost  all  the  gem  and  cavity  bearing  por- 
tions of  the  Maine  pegmatites  grade  into  normal  pegmatite  con- 
taining abundant  graphic  granite.  From  the  presence  of  cavities 
and  of  the  rare  minerals,  from  the  general  field  relations,  and  from 
the  fact  that  the  quartz  of  the  pockets  and  of  the  gem-bearing  por- 
tions, wherever  tested,  is  of  the  low-temperature  variety,  there  can 
be  no  reasonable  doubt  that  these  gem  and  cavity  bearing  portions 
rather  than  the  bordering  graphic  portions  were  the  last  parts  of 
the  pegmatite  to  crystallize.6 

In  considering  the  significance  of  the  graphic  intergrowths  found 
in  pegmatite,  it  is  necessary  to  consider  not  only  the  intergrowths 
of  feldspar  and  quartz,  but  also  the  almost  equally  regular  inter- 
growths of  muscovite  and  quartz,  garnet  and  quartz,  black  tourma- 
line and  quartz,  etc.  As  muscovite,  tourmaline,  and  garnet  are 
less  abundant  than  feldspar  in  the  pegmatites,  their  intergrowths 

a Op.  cit.,  pp.  118-123. 

ft  In  the  tourmaline-bearing  pegmatites  of  California  (according  to  W.  T.  Schaller,  oral  communication) 
the  zones  characterized  by  cavities  and  by  the  presence  of  the  gems  and  other  rare  minerals,  which  were 
almost  certainty  the  last  portions  to  crystallize,  grade  laterally  without  sharp  break  into  graphic  granite 
which  borders  one  wall  of  these  pegmatite  masses.  Occasional  stringers  of  pegmatite  bearing  lithium 
minerals  branch  off  from  the  main  gem-bearing  layer  and  cut  the  bordering  graphic  granite. 


GEOGRAPHIC  RELATIONS. 


43 


with  quartz  are  also  less  abundant  and  are  usually  of  smaller  size. 
Such  intergrowths  occur,  however,  scattered  irregularly  through 
practically  all  of  the  coarser  pegmatite  masses.  If  the  eutectic 
be  considered,  as  usual,  as  the  residue  of  uniform  composition  and 
minimum  freezing  point  which  is  the  last  portion  to  crystallize,  it 
is  "manifestly  impossible  to  regard  each  of  these  intergrowths  as 
representing  a eutectic  mixture,  unless  indeed  several  portions  of 
the  pegmatite  magma  are  regarded  as  crystallizing  more  or  less 
independently  of  the  remainder  of  the  mass. 

MINERALOGICAL  PROVINCES. 

It  has  already  been  pointed  out  that  most  of  the  known  pegmatites 
which  are  rich  in  sodium  and  lithium  minerals — that  is,  most  of  the 
gem-bearing  pegmatites — are  restricted  to  a zone  about  25  miles  long 
and  8 to  9 miles  in  width  extending  in  a northwesterly  direction  from 
Auburn  in  Androscoggin  County  to  Greenwood  in  Oxford  County. 
A second  and  much  smaller  area  includes  the  Newry  and  Black  Moun- 
tain localities  in  the  northern  part  of  Oxford  County  and  differs  from 
the  larger  area  in  that  the  gem  minerals  are  embedded  in  the  solid  peg- 
matite and  are  not  in  pockets.  Within  both  areas  the  lithium-bearing 
phases  form  only  a small  proportion  of  the  pegmatite  present,  most  of 
which  has  the  normal  composition.  The  occurrence  locally  of  certain 
masses  of  unusual  composition  is  to  be  attributed  either  to  the  exist- 
ence in  the  magma  of  sodium  and  lithium  in  very  minute  excess  over 
their  percentages-  in  bordering  pegmatite  magmas,  or  else  to  differing 
degrees  of  segregation  in  magmas  whose  average  composition  was 
similar.  As  already  explained,  quartz  associated  with  lepidolite  and 
clevelandite  from  the  gem-bearing  portion  of  one  of  these  pegmatites 
showed  low-temperature  characters,  and  the  unusual  abundance  of 
pockets  indicates  that  these  portions  were  richer  than  the  normal  in 
gaseous  constituents,  probably  mainly  water  vapor.  In  general, 
therefore,  the  gem-bearing  pegmatites  were  characterized  by  a higher 
percentage  of  sodium,  lithium,  and  phosphorus  than  the  normal  peg- 
matites, and  probably  by  more  water  vapor  and  a slightly  lower 
temperature  of  crystallization. 

The  region  characterized  by  pegmatites  rich  in  fluorine  minerals  but 
not  in  lithium  minerals  forms  an  area  only  a few  miles  across  in  the 
town  of  Stoneham  and  bordering  parts  of  other  towns  in  Oxford 
County,  Maine,  and  Chatham,  N.  H. 

GEOGRAPHIC  RELATIONS. 

The  broad  geographic  relationships  of  the  granites  and  pegmatites 
are  also  significant  of  their  relationship  and  origin.  As  may  be  seen 
from  Plate  I,  many  of  the  granite  areas  of  the  eastern  portion  of  Maine 
are  characterized  by  sharp  boundaries,  and  most  of  the  granite  areas 


44  PEGMATITES  AND  ASSOCIATED  BOCKS  OE  MAINE. 

of  southwestern  Maine  show  very  indefinite  boundaries  and  are  bor- 
dered by  large  areas  of  slates  and  schists  which  have  been  intruded  by 
various  amounts  of  granite  gneiss  and  pegmatite  and  by  some  granite 
and  diorite.  The  contrast  between  the  two  types  of  contacts  is  well 
shown  within  the  Penobscot  Bay  a and  Rockland  b quadrangles.  In 
many  parts  of  the  former  area,  notably  along  the  granite-schist  con- 
tact from  Bluehill  village  northward  and  from  Bluehill  Falls^south- 
westward  to  Sedgwick,  the  granite  preserves  its  normal  medium  grain 
up  to  the  exact  contact.  In  most  places  this  contact  is  so  sharp  that 
it  is  possible  to  stand  with  one  foot  resting  upon  typical  Ellsworth 
schist  and  the  other  foot  resting  upon  normal  granite.  Dikes  and 
irregular  intrusions  of  granite  are  not  very  abundant  in  the  schists 
near  the  main  granite  masses,  and  flow  gneiss,  pegmatite,  and  basic 
differentiations  from  the  granite  magma  are  almost  entirely  absent. 
In  the  Rockland  quadrangle,  on  the  other  hand,  the  contact  relations 
are  wholly  different,  the  change  from  pure  granite  to  pure  sediments 
taking  place  gradually  through  a transition  zone  of  contact-metamor- 
phosed and  injected  sediments  2 to  3 miles  in  width.  These  transi- 
tion zones  include  a great  variety  of  rocks,  slate,  schist,  injection 
gneiss,  flow  gneiss,  diorite,  diabase,  pegmatite,  and  granites  of  various 
textures  all  associated  in  a manner  so  that  it  is  impracticable  to 
delineate  them  separately  in  ordinary  geologic  mapping.  In  western 
and  southwestern  Maine  these  transition  zones  are  much  broader  than 
in  the  Rockland  quadrangle  and  contain  larger  amounts  of  pegmatite 
and  granite  gneiss  and  smaller  amounts  of  basic  igneous  rocks. 

The  contrast  between  the  sharpness  of  certain  granite  contacts 
observed  in  the  Bluehill  region  and  the  very  gradual  transitions 
observed  in  the  Rockland  quadrangle  and  farther  southwest  seem  to 
be  best  explained  on  the  hypothesis  that  the  broad  iqjected  zones 
represent  portions  of  the  “roof”  of  granite  batholiths,  whereas  the 
sharp  contacts  represent  the  sides  of  similar  batholiths.  The  char- 
acter of  the  rocks  found  in  the  two  types  of  contacts  lends  support  to 
this  view.  The  fact  that  water  gas  and  other  gases  and  their  dis- 
solved substances  escape  upward  more  readily  than  they  do  laterally 
may  explain  the  great  abundance  of  pegmatite  in  the  broad  transition 
zones,  inasmuch  as  the  presence  of  such  gases  is  believed  to  be  the 
most  important  factor  in  the  development  of  pegmatitic  texture.  It 
is  a reasonable  supposition  that  basic  differentiation  from  the  granitic 
magma  would  also  be  more  rapid  upward  than  laterally,  and  the 
abundance  of  diabase  and  diorite  in  certain  of  the  transition  zones 
may  thus  be  accounted  for.  The  hypothesis  is  also  in  accord  with 
the  low  temperatures  at  which  certain  portions  of  the  pegmatites 
appear  to  have  crystallized  in  comparison  with  the  temperatures  of 

a Folio  149,  Geol.  Atlas  U1S.,  U.  S.  Geol.  Survey. 

b Folio  158,  Geol.  Atlas  UJS.,  U.  S.  Geol.  Survey. 


GEOGRAPHIC  RELATIONS. 


45 


crystallization  of  normal  granites;  it  also  accords  with  the  presence 
of  numerous  dikes  of  very  fine-grained  granite,  some  so  fine  as  to 
be  rhyolitic  in  certain  of  the  contact  zones,  and  with  their  absence 
about  the  sharper  contacts. 

SUMMARY. 

Field  and  laboratory  studies  of  the  Maine  pegmatites  indicate  that 
all  are  in  a broad  way  contemporaneous  and  are  genetically  related 
to  the  associated  granites. 

External  conditions,  though  locally  having  some  slight  influence, 
are  not  primarily  the  cause  of  the  pegmatitic  textures.  The  presence 
of  the  rarer  elements  seems  to  have  had  only  a minor  influence  on 
the  texture,  for  in  many  typical  pegmatites  such  elements  appear  to 
be  entirely  absent.  Theoretical  considerations  and  the  presence  of 
miarolitic  cavities  in  certain  pegmatites  point  to  the  gaseous  con- 
stituents of  the  pegmatite  magmas,  especially  water  vapor,  as  the 
primary  cause  of  their  textures. 

Although  certain  facts,  such  as  the  pinch  and  swell  phenomena 
observed  in  many  pegmatite  dikes  in  contrast  with  the  parallel- 
walled  character  of  most  of  the  granite  dikes,  indicate  somewhat 
greater  mobility  in  the  pegmatite  than  in  the  granite  magmas,  other 
facts,  such  as  the  sharpness  of  many  of  the  contacts  between  pegma- 
tite and  schist,  the  absence  of  absorption  along  any  of  the  contacts, 
the  presence  of  angular  schist  fragments  now  surrounded  by  pegma- 
tite, the  small  proportion  by  volume  which  the  cavities  bear  to  the 
whole  pegmatite  mass,  the  absence  of  notably  greater  contact-meta- 
morphic  effects  near  pegmatite  than  near  granite  contacts,  and  the 
batholithic  dimensions  of  some  pegmatite  bodies,  all  suggest  that  the 
difference  in  average  composition  between  the  granite  pegmatites 
and  the  normal  granites  was  relatively  slight  and  that  the  pegmatite 
magmas  were  not  so  greatly  different  in  physical  characters  from  the 
granite  magmas  as  has  been  commonly  supposed. 

In  his  text-book  on  igneous  rocks  ° Iddings,  in  discussing  the  peg- 
matites, says  “the  amount  of  gases  concentrated  in  such  magmas 
was  not  many  times  that  of  the  gases  originally  distributed  through- 
out the  magma  from  which  the  pegmatite  was  differentiated;  pos- 
sibly not  more  than  ten  times  as  much.”  The  present  writer  would 
be  inclined,  in  the  case  at  least  of  the  granite  pegmatites  of  New 
England,  to  estimate  the  gaseous  content  of  these  rocks  at  a still 
lower  amount. 

The  experiments  of  Wright  and  Larsen  on  quartz  from  pegmatites 
from  Maine  and  elsewhere  indicate  that  some  at  least  of  the  coarser 
pegmatites  began  to  crystallize  at  a temperature  slightly  above  the 
inversion  point  of  quartz  (about  575°  C.)  and  completed  their  crystal- 


a Iddings,  J.  P.,  Igneous  rocks,  vol.  1,  1909,  p.  276. 


46 


PEGMATITES  AND  ASSOCIATED  ROCKS  OF  MAINE. 


lization  somewhat  below  this  temperature.  It  is  probable  that 
many  of  the  finer-grained  pegmatites  crystallized  wholly  above 
575°  C. 

The  theory  that  the  graphic  intergrowths  in  pegmatites  represent 
eutectic  mixtures  can  not  be  regarded  as  proved  by  the  published 
analyses.  Certain  field  evidence  is  unfavorable  to  the  eutectic 
theory. 

The  broader  field  relations  suggest  that  the  large  areas  character- 
ized by  particular  abundance  of  pegmatite  intrusions  constitute  in 
reality  the  roofs  overlying  granite  batholiths.  Where  more  exten- 
sive erosion  has  exposed  the  flanks  of  such  batholiths,  pegmatite 
masses  in  the  bordering  schists  are  not  abundant. 

LOCAL  DESCRIPTIONS. 

ANDROSCOGGIN  COUNTY. 

AUBURN. 

CHARACTER  AND  DISTRIBUTION  OF  THE  PEGMATITE. 

Large  areas  in  the  town  of  Auburn,  especially  in  the  valleys  of 
Androscoggin  and  Little  Androscoggin  rivers,  are  covered  with  sands 
of  glacial  origin  which  obscure  the  bed  rock.  Wherever  the  latter  is 
exposed,  however,  it  is  found  to  be  either  quartz-mica  schist  or  peg- 
matite intrusive  in  the  schist  or  a coarse  gneiss  resulting  from  a very 
intimate  injection  of  the  schist  by  pegmatite. 

Auburn  Falls. — The  prevailing  rock  types  and  the  relationships 
between  them  are  well  shown  in  the  river  bed  at  the  falls  just  above 
the  bridge  between  Auburn  and  Lewiston.  (See  p.  11  and  PL  III,  B.) 
The  purplish-gray , quartz-mica  schists,  which  dip  about  30°  NE.,  in 
many  places  show  distinct  bedding  and  are  of  undoubted  sedimentary 
origin.  They  are  similar  in  every  way  to  those  at  the  Auburn  res- 
ervoir. The  pegmatite  masses  are  intruded  in  general  parallel  to  the 
trend  of  the  schists.  Just  below  the  bridge  both  schists  and  peg- 
matite are  cut  by  a dike  of  fine-grained  diabase  3 to  4 feet  wide. 

The  largest  pegmatite  mass  exposed  crosses  the  river  bed  at  the 
falls,  which  are  a result  of  the  superior  resistance  to  erosion  offered 
by  this  pegmatite  and  its  bordering  intensely  injected  schists  as  com- 
pared with  the  ordinary  phases  of  the  schists.  This  pegmatite  sill 
has  a maximum  thickness  of  about  20  feet  and  extends  nearly  across 
the  river  bed,  though  it  forks  at  several  places.  It  preserves  about  the 
same  coarseness  in  the  wide  and  narrow  parts  and  in  the  center  and 
next  the  walls.  Its  contact  with  the  schist  is  everywhere  sharp,  and 
there  is  not  the  least  evidence  here  or  anywhere  in  this  vicinity  of  any 
absorption  of  schist  by  the  pegmatite. 

Auburn  reservoir. — Fresh  exposures  of  the  schists  were  also  beauti- 
fully shown  at  the  new  reservoir  site  on  Goff  Hill  in  Auburn.  This 


ANDKOSCOGGIN  COUNTY. 


47 


reservoir  was  under  construction  at  the  time  of  the  writer’s  visit,  and 
many  exposures  then  showing  have  since  been  covered.  The  schists, 
which  in  general  are  purplish  gray  in  color,  have  been  intensely 
injected  by  pegmatite,-  though  the  largest  pegmatite  lens  observed 
was  10  feet  long  and  2\  feet  in  greatest  width.  The  injection  does 
not  in  all  places  take  the  form  of  definite  lenses  or  stringers  of  peg- 
matite, but  in  many  the  impregnation  of  the  schist  is  so  intimate  as 
to  obscure  almost  entirely  the  schistose  structure  and  develop  a 
speckled  appearance.  The  sedimentary  origin  of  the  schist  is  shown 
by  the  general  evenness  and  regularity  of  its  trend  and  by  the  local 
preservation  of  bedding  in  its  more  quartzose  layers. 

Danville  Corners. — An  exposure  of  considerable  interest  was  ob- 
served in  a road  cut  about  half  a mile  southeast  of  Danville  Corners, 
where  the  rock,  which  has  been  recently  blasted,  is  for  the  most 
part  a gray  granite  of  slightly  gneissic  texture.  It  is  plianerocrys- 
talline,  most  of  its  mineral  grains  ranging  from  1 to  2 millimeters 
in  diameter  and  its  texture  is  typically  granitic.  The  faint  gneissic 
texture  is  due  to  a parallel  orientation  of  many  of  the  biotite  plates, 
to  their  slightly  greater  abundance  along  some  planes  than  along 
others,  and  to  slight  differences  in  the  coarseness  of  certain  bands  as 
compared  with  others.  Under  the  microscope  the  constituents  are 
seen  to  be  quartz,  ortlioclase  and  microcline,  albite,  biotite  (altering 
to  chlorite),  and  some  muscovite,  their  relative  abundance  appearing 
from  casual  examination  to  be  in  the  order  given. 

This  granite  gneiss  is  associated  with  subordinate  amounts  of  peg- 
matite, which  is  not  so  coarse  as  much  pegmatite  found  elsewhere,  but 
is  typically  pegmatitic  in  texture.  The  pegmatite  specimen  collected 
for  detailed  study  shows  feldspar  crystals  up  to  one-half  inch  across 
and  aggregates  of  feldspar  crystals  unmixed  with  other  constituents 
1 inch  across  and  areas  of  smoky  quartz  one-lialf  inch  across.  Mus- 
covite crystals  are  one-eighth  inch  across  and  biotite  crystals  one- 
fourth  inch.  Garnets  up  to  one-sixteenth  inch  in  diameter  occur. 
Texturally  the  pegmatite  differs  from  the  granite  gneiss  in  showing  a 
much  greater  range  in  size  in  the  mineral  grains  of  each  species  and 
much  less  evenness  in  their  distribution.  In  the  pegmatite  there  is 
a marked  tendency  toward  segregation  of  the  different  mineral  con- 
stituents, some  areas  being  dominantly  feldspar  and  others  domi- 
nantly quartz.  This  feature  is  entirely  distinct  from  mere  increased 
coarseness  of  grain. 

The  constituents  of  the  pegmatite  are  identical  with  those  of  the 
granite  gneiss,  being  (1)  quartz,  (2)  ortlioclase  and  microcline,  (3)  oligo- 
clase-albite  with  some  border  rims  of  albite,  (4)  biotite,  and  (5)  musco- 
vite, the  numbers  showing  the  order  of  their  apparent  abundance.  The 
principal  difference  in  their  mineral  composition  is  the  much  smaller 
quantity  of  biotite  present  in  the  pegmatite.  Inclusions  are  abundant 


48 


PEGMATITES  AND  ASSOCIATED  ROCKS  OF  MAINE. 


in  the  quartzes  of  both  rocks  and  are  of  about  the  same  size.  The 
majority  are  under  0.005  millimeter,  but  a few  are  over  0.01  millimeter 
in  greatest  dimension.  They  are  not  notably  more  abundant  in  the 
pegmatite  than  in  the  granite  gneiss. 

In  a few  places  the  pegmatite  is  rather  sharply  delimited  from  the 
granite  gneiss  in  dikelike  masses,  but  for  the  most  part  it  occurs  in 
the  granite  in  lens-shaped  or  roughly  spheroidal  masses  from  a few 
inches  to  a foot  or  more  across,  coarsest  in  the  center  and  grading  very 
gradually  with  increasing  fineness  into  the  surrounding  granite  gneiss. 
A few  of  the  pegmatite' “bunches”  show  a center  composed  largely  of 
quartz,  surrounded  by  a zone  in  which  feldspar  is  dominant.  In 
places  the  pegmatite  masses  send  off  irregular  and  vaguely  bounded 
ramifications  into  the  granite  gneiss.  The  two  types  are  associated  in 
the  most  irregular  manner.  In  places  the  pegmatite  is  very  coarse 
and  carries  beryl  and  black  tourmaline.  One  feldspar  crystal  in  this 
portion  measured  8 inches  across. 

The  relation  and  mineral  characters  detailed  above  suggest  the 
following  inferences  in  regard  to  the  genesis  of  the  rocks  described: 

1.  The  presence  of  the  same  mineral  species  in  the  same  order  of 
abundance  in  both  rocks  and  the  many  instances  of  complete  grada- 
tion of  one  rock  into  the  other  show  that  they  are  products  of  the 
same  parent  magma. 

2.  The  fact  that  the  pegmatite  masses  in  some  parts  of  their  length 
have  rather  sharp  walls  and  in  other  parts  grade  gradually  into  the 
granite  gneiss  indicates  that  certain  portions  of  the  pegmatite  crys- 
tallized after  some  of  the  granite  was  rigid  enough  to  develop  cracks 
into  which  the  pegmatite  magma  penetrated,  and  that  at  the  same 
time  other  parts  were  fluid  enough  to  permit  pegmatite  and  granite 
to  solidify  with  gradual  gradation  and  perfect  crystallographic  con- 
tinuity between  them. 

3.  The  intimate  and  small-scale  manner  in  which  the  pegmatite 
and  the  granite  gneiss  are  associated,  and  the  fact  that  these  varia- 
tions are  so  irregular  and  are  not  related  in  any.  way  to  any  wall 
rock  now  observed  or  probably  existent  in  the  past,  suggest  that  the 
causes  operative  in  producing  the  variations  in  texture  and  composi- 
tion were  not  of  external  origin,  but  were  inherent  in  the  magma  itself. 

Danville  Junction. — In  the  extreme  western  part  of  the  town  of 
Auburn,  about  3 miles  west  of  Danville  Junction,  along  the  road  to 
Poland  Springs,  conspicuous  white  ledges  of  pegmatite  exemplify 
clearly  certain  common  relationships  of  the  pegmatites  of  this  part 
of  the  State.  In  places  this  pegmatite  grades  gradually  with  perfect 
crystallographic  continuity  into  a rather  fine-grained  granite  gneiss. 
One  pegmatitic  band  1 inch  wide  in  this  granite  gneiss  shows  contor- 
tions, which,  in  the  absence  of  any  regional  metamorphism  later 
than  the  granite-pegmatite  intrusions,  appear  only  explainable  as  the 


ANDKOSCOGGIN  COUNTY. 


49 


result  of  flowing  movements  in  the  granite  gneiss  at  the  time  the 
pegmatite  was  intruded.  A small  mass  of  quartz-mica  schist  lying 
between  two  sill-like  masses  of  pegmatite,  though  evidently  molded 
somewhat  during  their  intrusion,  shows  no  evidence  of  absorption. 
Some  of  the  narrower  pegmatite  bands  in  the  schists  can  be  traced 
continuously  through  portions  showing  successively  larger  propor- 
tions of  quartz  into  ulit-par-lit  ” injections  of  pure  quartz.  Several 
diabase  dikes  at  this  locality  strike  N.  70°  to  80°  W.  and  dip  ver- 
tical; they  are  about  parallel  to  the  most  prominent  joint  planes  in 
the  granite  and  pegmatite. 

The  inferences  which  appear  justified  from  the  relations  just 
described  are  as  follows: 

1.  The  complete  and  gradual  gradation  of  pegmatite  into  granite 
gneiss  and  the  presence  of  contorted  bands  of  pegmatite  in  the  granite 
indicate  that  portions  at  least  of  the  granite  gneiss  were  still  more 
or  less  fluid  when  the  pegmatite  was  intruded. 

2.  Certain  quartz  stringers  in  the  schists  are  the  end  products  of 
pegmatitic  crystallization. 

3.  Neither  the  granite  gneiss  nor  the  pegmatite  at  this  locality 
exercised  any  considerable  absorptive  action  on  the  quartz-mica 
schists  into  which  they  were  intruded. 

Mount  Apatite. — Pegmatite  deposits  are  worked  extensively  for 
feldspar,  and  to  some  extent  for  minerals  valuable  as  gems  or  as 
cabinet  specimens,  at  Mount  Apatite,  a low  prominence  about  6 miles 
west  of  the  city  of  Auburn  near  the  road  to  Minot,  and  about  2 miles 
from  Littlefield,  the  nearest  railroad  station  on  the  Lewiston  branch 
of  the  Grand  Trunk  Railway. 

The  interest  in  Mount  Apatite  as  a mineral  locality  may  be  said 
to  date  back  to  1868,  when  the  Rev.  Luther  Hills  called  attention  to 
a specimen  of  tourmaline  found  by  G.  C.  Hatch  on  his  farm.  This 
crystal  yielded  a fine  2-carat  gem  of  light-green  color,  but  it  was  not 
found  in  place,  and  considerable  searching  having  failed  to  reveal 
any  further  crystals  the  property  remained' unworked  for  some  years. 
In  1883  N.  H.  Perry,  of  South  Paris,  found  the  tourmalines  in  place 
near  the  Hatch  farmhouse,  and  in  that  year,  from  an  excavation 
about  20  by  8 feet  and  8 feet  deep,  took  nearly  1,500  tourmaline 
crystals,  ranging  from  very  small  ones  1 centimeter  long  to  one  10£ 
centimeters  long.  Thomas  F.  Lamb,  of  Portland,  was  also  one  of 
the  pioneers  at  this  locality,  working  intermittently  for  three  or  four 
years,  part  of  the  time  with  Loren  B.  Merrill,  of  Paris,  now  the  pro- 
prietor of  the  Mount  Mica  tourmaline  mine.  Pie  found  a consider- 
able number  of  gem  tourmalines  and  some  remarkably  handsome 
groups  of  crystals  of  smoky  quartz,  besides  much  valuable  cabinet- 
specimen  material. 

63096°— Bull.  445—11 4 


50 


PEGMATITES  AND  ASSOCIATED  ROCKS  OF  MAINE. 


After  the  expiration  of  the  leases  of  the  persons  mentioned,  no 
mining  of  importance  was  done  at  Mount  Apatite  until  1902,  when 
the  Maine  Feldspar  Company,  now  the  largest  operator  at  this  locality, 
commenced  mining  feldspar  for  use  in  pottery  manufacture.  Pre- 
viously small  amounts  of  quartz  had  been  mined  and  shipped  for 
use  in  the  manufacture  of  sandpaper,  and  it  is  interesting  to  note 
that  at  this  time  the  feldspar  was  considered  to  be  of  no  value  and 
was  thrown  on  the  dump  piles.  Although  a few  gems  and  cabinet 
specimens  have  been  found  in  the  course  of  the  feldspar  mining  and 
by  collectors  paying  short  visits  to  Mount  Apatite,  regular  mining 
for  gems  was  not  resumed  until  1907,  when  J.  S.  Towne  commenced 
operations  at  a new  locality  (p.  55). 

QUARRIES. 

Maine  Feldspar  Company  quarry  and  mill. — The  largest  workings  at 
Mount  Apatite  are  those  of  the  Maine  Feldspar  Company,  of  Auburn, 
which  commenced  operations  in  1902  and  has  operated  continuously 
to  the  present  time  (1909).  The  property  was  visited  by  the  writer 
in  August,  1906,  and  again  in  October,  1907. 

The  workings  consist  of  a number  of  small  pits  75  to  150  feet  long, 
50  feet  in  average  width,  and  10  to  20  feet  in  depth.  These  are  either 
close  together  or  partly  connected  and  are  located  in  a single  mass  of 
pegmatite  which  constitutes  the  summit  of  the  hill.  Much  of  the 
hilltop  is  bare,  but  in  a few  places  as  much  as  6 feet  of  clayey  till  must 
be  stripped  in  working. 

The  minerals  present  are  those  usually  found  in  the  granite  pegma- 
tites of  the  Atlantic  States  which  are  worked  for  feldspar  but  include 
many  others  that  are  characteristic  only  of  the  gem-bearing  pegma- 
tites. 

Quartz  varies  from  white  to  dark  gray  in  color  and  from  opaque  to 
beautifully  transparent.  Its  commonest  occurrence  is  in  graphic 
intergrowth  with  feldspar,  but  it  is  found  also  in  large  pure  masses 
and  in  clusters  of  beautiful  crystals  projecting  inward  from  the  walls 
of  pockets  or  fallen  into  the  mass  of  kaolin,  cookeite,  etc.,  at  their 
bottoms.  Many  of  these  groups  of  crystals  are  colorless  and  trans- 
parent, but  others,  notably  some  found  by  Thomas  F.  Lamb  in  one 
of  the  early  workings  near  the  Hatch  farmhouse,  though  transparent, 
are  smoky.  Some  of  these  latter  are  20  centimeters  in  length  and 
many  are  coated,  especially  at  the  tips  of  the  pyramids,  with  thin 
white  opaque  quartz,  which  is  plainly  of  more  recent'  development 
than  the  main  mass  of  the  crystal.  A few  of  the  quartz  crystals  of 
the  pockets  are  penetrated  by  small  colored  tourmaline  crystals.  The 
quartz  obtained  in  the  course  of  the  present  mining  for  feldspar  is 
white  and  very  pure  and  is  of  excellent  quality  for  any  of  the  many 
purposes  for  which  crystalline  quartz  is  now  used.  It  is  saved  in 


ANDROSCOGGIN  COUNTY. 


51 


stock  piles,  where  it  is  allowed  to  accumulate  until  a sufficient  amount 
is  obtained  to  make  its  shipment  worth  while.  The  profit  is  very 
small  in  handling  quartz  so  far  from  the  principal  markets  in  the 
Middle  Atlantic  States.  At  the  time  of  the  writer’s  visit,  in  1906, 
about  300  tons  of  it  was  lying  in  stock  piles. 

The  feldspar  is  mostly  buff  to  cream  colored  with  local  bluish- 
gray  spots  and  streaks  due  to  minute  inclusions.  Microscopic  study 
shows  it  to  consist  of  the  potash  varieties,  orthoclase  and  microcline, 
minutely  (perthitically)  intergrown  with  small  amounts  of  the  soda 
feldspar,  albite.  In  certain  narrow  and  irregular  bands  in  the  pegma- 
tite, albite  of  a dirty  olive-green  color  in  irregularly  bounded  crystals 
up  to  2 inches  in  length  is  almost  the  only  feldspar  present  and  is 
associated  with  quartz  and  muscovite.  As  is  usual  in  all  feldspar 
quarries,  most  of  the  material  marketed  under  the  commercial 
name  11  feldspar”  is  a graphic  intergrowth  of  feldspar  and  quartz, 
though  whatever  pure  feldspar  may  be  found  is  mixed  with  this. 
In  those  portions  of  the' pegmatite  which  bear  pockets,  the  white- 
bladed  variety  of  albite  known  as  clevelandite  is  very  abundant  in 
radiating  aggregates  of  thin  plates.  The  standard  or  No.  2 grade 
obtained  at  this  quarry  consists  principally  of  graphic  granite  with  a 
subordinate  amount  of  pure  feldspar.  Some  No.  1 grade  nearly  free 
from  quartz  is  also  obtained;  an  analysis  of  a sample  of  this,  made  in 
the  laboratory  of  the  United  States  Geological  Survey,  is  given  below. 

Analysis  of  No.  1 ground  feldspar  from  Auburn , Me. 


Silica  (Si02) 65.73 

Alumina  (A1203) « 19.  28 

Magnesia  (MgO) None. 

Lime  (CaO) 22 

Potash  (K20) 10.  26 

Soda  (Na20) 4.08 

Water  (H20) 48 


100.  05 


The  mineral  composition  of  this  sample,  as  calculated  from  the 
analysis,  is  as  follows: 


Mineral  composition  of  No.  1 ground  feldspar  from  Auburn,  Me. 


Quartz 

Orthoclase  and  microcline 

Albite 

Water 

Other  constituents 


2.  22 
60.  60 
35.  69 
.48 
1.02 


100.  01 

Muscovite  is  moderately  abundant,  but  almost  none  of  it  is  in  clear 
transparent  plates.  Most  of  it  is  of  the  A variety  (see  p.  139)  and  some 
of  the  bladelike  books  are  as  much  as  a foot  in  length.  It  is  common 


a Includes  traces  of  iron  and  any  Ti02  and  P205  that  may  be  present. 


52 


PEGMATITES  AND  ASSOCIATED  EOCKS  OF  MAINE. 


in  graphic  intergrowths  with  quartz.  As  described  below,  some  small 
clear  muscovite  prisms  are  surrounded  by  a border  of  lepidolite.  Mr. 
Lamb  has  also  found  some  fine  curved  crystals  of  muscovite. 

Biotite  is  abundant  only  locally  and  can  in  most  areas  be  readily 
avoided  in  mining  the  feldspar.  It  forms  typical  lath-shaped  crystals. 

Lepidolite  is  not  very  abundant,  but  some  occurs  especially  asso- 
ciated with  clevelandite  and  muscovite  near  pockets.  It  is  present 
in  granular  aggregates  of  small  plates  and  prisms  (in  many  places 
intergrown  with  some  quartz)  and  also  in  larger  plates.  Its  occur- 
rence as  narrow  borders  surrounding  muscovite  and  in  crystallo- 
grapliically  parallel  growth  with  it  has  been  fully  described  and 
figured  by  Clarke,0  who  gives  analyses  of  both  of  the  muscovite  and 
the  lepidolite  border. 

Garnets  of  small  size  occur  sparsely  in  all  parts  of  the  pegmatite. 
They  are  most  abundant  in  the  more  quartzose  and  micaceous  parts 
and  are  not  present  in  injurious  amounts  in  the  more  highly  f eld- 
spathic  portions. 

Black  tourmaline  is  present  in  all  those  portions  of  the  pegmatite 
which  carry  colored  tourmalines  but  is  only  locally  abundant  and  is 
not  particularly  bothersome  in  feldspar  mining.  Most  of  the  colored 
tourmalines  which  have  been  obtained  have  come,  not  from  the 
feldspar  workings,  but  from  small  pits  near  the  Hatch  farmhouse, 
worked  at  an  earlier  date  solely  for  their  gems  and  mineral  specimens. 
Those  found  in  1883  by  N.  H.  Perry  ranged  from  1 centimeter  to 
10 \ centimeters  long,  and  differ  from  the  majority  of  the  Maine 
tourmalines  in  being  mostly  of  lighter  color.  They  were  found 
colorless,  light  pink,  lilac,  light  blue,  light  puce  colored,  bluish  pink, 
and  light  green,  some  single  crystals  showing  nearly  all  these  colors. 
Gems  from  some  of  the  paler  crystals  are  said  to  have  deepened  very 
much  in  color  after  cutting.  The  majority  of  these  crystals,  of  which 
nearly  1,500  were  obtained,  were  more  or  less  flawed.  Some  of  the 
tourmalines  found  later  by  Mr.  Lamb  were  cut  into  gems  of  emerald- 
green  color. 

Crystals  of  light  bluish-green  beryl  also  occur  rather  abundantly, 
embedded  in  the  solid  pegmatite.  One  hexagonal  beryl  found  about 
1898  is  reported  by  J.  S.  Towne  to  have  been  4 feet  in  diameter  and 
20  feet  in  length,  but  the  majority  do  not  exceed  1 foot  in  length  and 
a few  inches  in  diameter.  Near  the  gigantic  beryl  mentioned 
occurred  several  pockets  bearing  the  finest  crystals  of  herderite  ever 
found  on  Mount  Apatite;  the  form  and  composition  of  these  have  been 
described  by  Penfield.6 

Apatite  occurs  occasionally  in  crystals  of  fine  luster  and  trans- 
parency, the  colors  being  light  pink,  purple,  light  blue,  and  blue 


a Clarke,  F.  W.,  The  lepidolites  of  Maine:  Bull.  U.  S.  Geol.  Survey  No.  42,  1887,  pp.  15-17. 
b Penfleld,  S.  L.,  Herderite  from  Auburn,  Me.:  Am.  Jour.  Sci.,  3d  ser.,  vol.  47,  1894,  p.  336. 


ANDROSCOGGIN  COUNTY. 


53 


green.  The  crystals  occur  singly  or  in  groups  and  vary  in  size  from 
1 mm.  to  15  mm.  long  and  from  1 to  20  mm.  wide. 

Other  minerals  reported  a from  Mount  Apatite  are  allanite,  amblyg™ 
onite,  autunite,  cassiterite,  columbite,  cookeite,  damourite,  gummite, 
magnetite,  molybdenite,  triplite,  and  zircon. 

Neither  the  exact  form  nor  the  area  of  the  pegmatite  body  could 
be  determined,  but  it  occupies  practically  the  whole  top  of  Mount 
Apatite,  and  it  is  probable  that  further  stripping  of  the  soil  in  the  • 
neighborhood  of  the  present  workings  will  disclose  considerable 
amounts  of  commercially  valuable  feldspar  and  possibly  portions 
valuable  enough  to  be  worked  for  their  gem  minerals.  The  presence 
in  the  pegmatite  of  one  of  the  northern  pits  of  a 2-foot  band  of 
epidotized  altered  quartzite  which  is  nearly  flat  lying  and  is  regarded 
as  a remnant  of  the  sediments  into  which  the  pegmatite  was  intruded, 
and  the  presence  in  other  pits  of  this  quarry  and  in  the  neighboring 
quarries  of  nearly  flat-lying  bands  particularly  rich  in  small  garnets, 
both  indicate  that  the  general  attitude  of  the  whole  pegmatite  mass 
is  rather  flat  lying. 

On  the  floor  of  one  of  the  pits  is  exposed  an  instructive  cross  section 
of  a dike  of  pegmatite  cutting  the  main  pegmatite  mass.  This  dike 
is  a foot  in  width  and  cuts  graphic  granite  whose  usual  variations  of 
texture  are  wholly  unaffected,  although  the  two  rocks  show  crystal- 
lographic continuity  along  the  immediate  contact.  The  dike  at  its 
borders  is  mainly  feldspar,  the  separate  more  or  less  blade-shaped 
crystals  being  disposed  at  right  angles  to  the  walls.  The  center  of 
the  dike  is  an  irregular  band  of  light-gray  quartz.  The  dike  was 
probably  intruded  soon  after  the  partial  or  complete  solidification  of 
the  main  mass  of  pegmatite  under  conditions  favoring  more  segrega- 
tion of  the  quartz  and  feldspar  than  usually  took  place.  Only  one 
other  dike  of  similar  character  was  observed  by  the  writer  in  the 
course  of  two  months’  field  study.  Their  rarity  argues  for  the 
essential  contemporaneity  of  most  of  the  pegmatite  intrusions. 

Pockets  are  of  rather  rare  and  irregular  occurrence  and  are  found 
only  in  the  coarser  portions  of  the  deposit.  Very  few  were  observed 
by  the  writer.  Most  of  them  are  said  to  be  under  1 foot  in  diameter, 
but  one  about  4 by  6 by  5 feet  in  size  is  said  to  have  been  found. 
Clear  crystalline  quartz  is  the  commonest  mineral  found  in  the  pock- 
ets, though  some  tourmalines  and  beryls  of  gem  quality  and  crystals 
of  herderite  occur:  Here,  as  at  other  localities,  the  clevelandite  variety 
of  albite  is  common  near  the  pockets. 

Several  dikes  of  typical  fine-grained  diabase,  whose  minerals  under 
the  microscope  show  only  slight  alteration,  cut  the  pegmatite.  One 
observed  was  20  feet  in  width  and  another  6 feet  in  width. 


a Kunz,  G.  F.,  On  the  tourmalines  and  associated  minerals  of  Auburn,  Me.:  Am.  Jour.  Sci.,  3d  ser., 
vol.  27,  1884,  pp.  303-305. 


54 


PEGMATITES  AND  ASSOCIATED  HOCKS  OF  MAINE. 


The  topographic  situation  of  this  deposit  on  the  crest  of  the  hill 
favors  the  ready  disposition  of  the  waste  from  the  quarries  and  also 
provides  a down-hill  haul  most  of  the  way  from  the  quarry  to  the 
mill.  The  excavating  is  accomplished  by  steam  drilling  and  blasting, 
the  material  then  being  broken  up  with  sledges  and  picked  over  by 
hand.  It  is  hauled  2 miles  by  teams  to  the  mill  at  Littlefield  station. 
The  usual  force  consists  of  a foreman  and  10  laborers. 

The  feldspar  quarried  at  Mount  Apatite  is  ground  at  a mill  located 
at  the  side  of  the  Grand  Trunk  Railway  at  Littlefield  station.  The 
ground  spar  is  loaded  directly  into  cars  at  the  mill  and  shipped 
in  bulk  mainly  to  potters  at  Trenton,  N.  J.,  and  East  Liverpool, 
Ohio.  The  equipment  consists  of  one  chaser  mill,  in  which  each 
stone  weighs  about  3J  tons,  and  a ball  mill,  which  is  larger  than 
that  used  at  most  feldspar  mills,  grinding  3 tons  at  a load;  the 
capacity  of  the  plant  is  about  15  tons  in  twenty-four  hours.  Eight 
men  and  a foreman  are  employed.  The  power  is  supplied  by  a 75- 
horsepower  Westinghouse  motor,  the  current  coming  from  a power 
plant  on  Androscoggin  River. 

Turner  feldspar  quarries. — Three  small  pits  on  the  southern  part  of 
the  summit  of  Mount  Apatite  have  been  worked  intermittently  during 
the  past  ten  years  by  E.  Y.  Turner,  of  Auburn,  the  product  being 
ground  principally  at  the  mill  of  the  Maine  Feldspar  Company.  The 
quarries  were  idle  at  the  time  of  the  writer’s  visits  in  1906  and  1907, 
but  had  been  worked  more  or  less  at  other  times  during  these  years. 
The  total  amount  of  material  which  has  been  taken  out  is  small. 

The  westernmost  pit  is  a nearly  circular  opening  25  feet  in  diameter 
and  about  10  feet  in  maximum  depth.  Most  of  the  rock  is  crowded 
with  blades  of  biotite  and  is  therefore  commercially  valueless,  though 
a small  amount  of  feldspar  free  from  iron-bearing  minerals  is  exposed 
on  the  floor  of  the  pit.  Some  black  tourmaline  occurs,  and  rosette- 
shaped graphic  intergrowths  of  quartz  and  muscovite  are  common. 

The  easternmost  pit  is  about  75  feet  long  by  30  feet  wide  and  10 
feet  in  maximum  depth.  At  this  pit  two  distinct  bands,  rich  in 
small,  dark-red,  opaque  garnets,  run  through  the  pegmatite;  they 
are  from  1 to  6 feet  apart  and  dip  about  15°  NW.  Another  zone 
about  1 foot  thick  lying  just  above  the  garnetiferous  zone  is  particu- 
larly rich  in  black  tourmaline,  and  above  this  is  a 4-foot  zone  which 
shows  an  unusual  profusion  of  muscovite  and  biotite  crystals.  The 
5 feet  of  pegmatite  below  the  garnetiferous  bands  contains  much 
feldspar  of  good  commercial  quality,  iron-bearing  minerals  being 
rare.  None  of  the  upper  layers  at  this  quarry  will  yield  feldspar 
suitable  for  pottery  purposes,  and  the  expense  of  removing  the  upper 
layers  would  probably  render  it  unprofitable  to  work  the  layer  of 
better  quality  at  the  bottom  of  the  pit. 


ANDROSCOGGIN  COUNTY. 


55 


A third  small  pit,  40  by  40  feet  and  8 feet  in  average  depth,  just 
north  of  the  one  described,  shows  some  feldspar  of  commercial  grade, 
as  does  also  a small  prospect  pit  on  the  southeastern  slope  of  the  hill. 
In  the  unopened  natural  exposures  near  these  quarries  practically 
all  the  rock  is  too  fine  grained  or  too  rich  in  muscovite  or  iron-bearing 
minerals  to  be  valuable  for  pottery  purposes.  As  far,  therefore,  as 
can  be  judged  from  the  present  exposures  these  quarries  show  little 
prospect  of  yielding  much  feldspar  of  pottery  grade.  The  material 
may  ultimately  prove  of  value  for  poultry  grit,  fertilizer,  or  other 
uses  where  iron-bearing  minerals  are  not  detrimental. 

The  pegmatite  of  these  quarries,  though  of  poorer  quality  com- 
mercially than  that  at  the  quarries  of  the  Maine  Feldspar  Company, 
appears  to  form  a part  of  the  same  large  pegmatite  mass.  The 
excavating  has  been  in  part  by  hand  drilling  and  blasting  and  in  part 
by  steam  drilling.  The  equipment  includes  a small  derrick. 

Towne  feldspar  and  gem  quarry. — In  April,  1907,  a quarry  was 
opened  by  J.  S.  Towne,  of  Brunswick,  Me.,  on  the  Pulsifer  farm  about 
one-half  mile  northwest  of  the  Maine  Feldspar  Company’s  quarries 
on  Mount  Apatite.  This  quarry  is  operated  by  the  Maine  Feldspar 
Company  for  feldspar,  the  gems  found  being  handled  by  Mr.  Towne. 

The  workings  were  visited  by  the  writer  in  October,  1907,  at  which 
time  they  consisted  of  three  very  small  pits  all  on  the  same  half  acre. 
All  are  in  pegmatite  but  only  two  expose  the  pockety  or  gem-bearing 
zone.  The  third  pit  is  higher  on  the  hill  slope,  and  has  not  yet  got 
down  to  the  pocket-bearing  layer;  in  the  lower  pits  it  has  penetrated 
it  for  4 feet  but  has  not  yet  reached  its  base.  The  gem-bearing  layer, 
though  grading  gradually  into  the  other  pegmatite,  is  distinguish- 
able from  it  not  only  by  the  presence  of  pockets  but  by  being  some- 
what coarser  than  other  portions  of  the  pegmatite.  It  is  characterized 
by  the  presence  of  clevelandite,  lepidolite,  and  green  tourmaline 
embedded  in  the  solid  pegmatite,  the  usual  “ indicators”  of  prox- 
imity to  gem  tourmalines.  The  pocket-bearing  layer  appears  to  dip 
about  10°  E.  The  bordering  schists  are  not  exposed  in  the  vicinity 
of  this  quarry. 

The  feldspar  obtained  from  these  pits  is  similar  to  that  mined  at 
the  Maine  Feldspar  Company’s  quarry,  and  of  equal  value.  Black 
tourmaline  is  abundant  near  many  of  the  pockets,  as  is  also  green  tour- 
maline in  semitransparent  crystals  up  to  one-eighth  inch  in  diameter, 
penetrating  or  interleaved  with  muscovite.  As  at  most  localities 
where  gem  tourmalines  are  found,  biotit e is  almost  entirely  absent. 
Garnets  are  not  abundant  in  the  pocket-bearing  layer,  though  fairly 
abundant  in  the  bordering  phases  of  the  pegmatite.  Lepidolite 
occurs  both  in  granular  aggregates  of  small  scales  and  prisms  and  in 
large  curved  crystals  with  rounded  botryoidal  surfaces  one-half  inch 


56 


PEGMATITES  AND  ASSOCIATED  ROCKS  OF  MAINE. 


to  1J  inches'  across;  many  of  its  curved  crystals  are  interlaminated 
with  the  bladelike  crystals  of  snow-white  clevelandite  or  are  partly 
embedded  in  light-gray,  more  or  less  transparent  quartz.  Amblygo- 
nite  occurs  in  the  solid  pegmatite  in  irregular  masses,  some  of  them 
6 to  8 inches  across.  Some  small  crystals  of  columbite,  cassiterite, 
and  rhodochrosite  occur,  but  their  crystal  faces  are  usually  only 
imperfectly  developed.  One  crystal  of  zinc  spinel  of  perfect  form, 
five-eighths  inch  in  diameter,  was  found  embedded  in  the  feldspar. 
At  the  time  of  the  writer’s  visit  only  two  gem-bearing  pockets  had 
been  found.  One  of  these  bore  dark  grass-green  tourmalines  and  the 
other  light-green  tourmalines  tipped  with  opaque  pink.  The  largest 
of  the  dark-green  tourmalines  was  about  three-fourths  inch  in 
diameter  and  1J  inches  long  but  was  badly  flawed.  A number  of 
other  pockets  bore  only  crystals  of  transparent  quartz.  Some  fine 
specimens  of  herderite  have  also  been  found  at  this  locality.  This 
mineral  occurs  in  short  prisms,  few  of  them  over  one-fourth  inch  long, 
commonly  as  an  incrustation  on  the  quartz  crystals  of  the  pockets. 
One  short  stout  crystal  attached  to  muscovite  was  as  large  as  the 
end  of  one’s  thumb.  This  mode  of  occurrence  is  similar  to  that 
observed  at  Stoneham,  where  it  was  first  discovered,  and  there  can 
be  little  doubt  that  it  was  formed  through  gaseous  or  aqueous 
deposition  after  the  solidification  of  the  main  pegmatite  mass. 

The  feldspar  obtained  at  this  locality  is  hauled  2 miles  for  grinding 
to  the  mill  of  the  Maine  Feldspar  Company.  The  gem  tourmalines 
are  cut  and  sold,  principally  in  Maine,  by  Mr.  Towne. 

Wade  and  Pulsifer  gem  quarries. — A pegmatite  mass  located  on 
the  farm  of  P.  P.  Pulsifer,  within  100  yards  of  the  Towne  quarry, 
was  opened  up  in  1901  and  was  worked  intermittently  until  1904 
for  its  gems  and  other  rare  minerals. 

The  quarry  was  visited  by  the  writer  in  August,  1906.  The  original 
pit,  opened  by  Mr.  Pulsifer  in  1901,  is  about  25  by  25  feet  and  8 feet 
deep;  it  connects  with  another  pit  about  75  by  30  feet,  with  a maxi- 
mum depth  of  8 feet.  The  mineral  rights  at  this  second  pit  were 
acquired  from  Mr.  Pulsifer  by  the  Maine  Tourmaline  Company,  and 
were  worked  in  the  summers  of  T904  and  1905. a The  two  pits  con- 
stitute virtually  a single  quarry. 

The  rock  at  this  locality  is  practically  bare,  so  that  little  or  no 
stripping  is  necessary  in  working  the  deposit.  The  pegmatite  is 
similar  in  general  character  to  most  of  the  gem-bearing  pegmatites 
of  the  State.  The  main  mass  of  the  rock  is  a graphic  intergrowth 
of  quartz  with  orthoclase  and  microcline,  showing  abrupt  variations 
in  coarseness.  The  deposit  as  a whole  seems  to  be  rather  flat 
lying,  as  is  shown  by  the  presence  near  its  base  of  a nearly  horizontal 

a Wade,  W.  R.,  The  gein-bearing  pegmatites  of  western  Maine:  Eng.  and  Min.  Jour.,  vol.  87,  1909, 
pp.  1127-1129. 


ANDROSCOGGIN  COUNTY. 


57 


garnetiferous  layer,  with  more  or  less  wavy  upper  surface,  which 
could  be  traced  continuously  for  over  50  feet.  The  garnetiferous 
band  itself  is  nowhere  over  1 $ inches  wide  and  is  a rather  finely  gran- 
ular crystallization  of  quartz,  feldspar,  and  garnet,  the  crystals  of 
garnet  constituting  about  half  of  the  band,  but  few  of  them  exceed- 
ing one-fourth  inch  in  diameter.  In  places  the  main  garnet  layer  is 
paralleled  below  at  a distance  of  1 to  2 inches  by  another  similar 
band  less  rich  in  garnets.  Outside  these  bands  garnet  occurs  in  the 
pegmatite  in  graphic  intergrowth  with  quartz  and  in  small  irregular 
masses  between  the  other  minerals.  The  pegmatite  shows  very 
different  characters  below  and  above  these  garnetiferous  layers. 
The  rock  just  above  is  much  coarser,  does  not  show  graphic  texture, 
and  does  show  albite,  in  part  massive  and  in  part  of  the  clevelandite 
variety,  as  its  dominant  feldspar,  though  it  contains  also  some  ortho- 
clase  in  graphic  intergrowth  with  quartz.  Muscovite  in  brush-shaped 
and  rosette-shaped  intergrowths  with  quartz  is  also  more  abundant 
above,  than  below  the  garnet  layer,  and  black  tourmaline  is  common  in 
places  in  graphic  intergrowth  with  quartz.  The  pegmatite  just  below 
the  garnetiferous  band  is  a rather  fine-grained  graphic  intergrowth 
of  quartz  and  orthoclase  showing  a more  or  less  radial  structure 
trending  about  at  right  angles  to  the  garnetiferous  layer. 

Only  small  portions  of  the  feldspar  are  of  commercial  grade  for 
pottery  purposes,  both  muscovite  and  biotite  being  quite  abundant. 

Quartz  is  mainly  present  in  intergrowth  with  other  minerals  or 
as  crystals  developed  on  the  walls  of  the  pockets.  Most  of  it  is  white 
or  light  gray,  but  some  small  amounts  of  rose  quartz  are  found. 

The  muscovite  commonly  occurs  with  quartz  in  brush-shaped 
or  rosette-shaped  intergrowths  averaging  4 to  5 inches  in  diameter 
and  disposed  with  utter  irregularity  throughout  the  pegmatite  mass. 
Some  of  these  grade  at  their  outer  borders  into  spearhead-shaped 
bundles  of  muscovite  penetrating  the  neighboring  quartz  masses, 
the  latter  being  apparently  continuous  with  the  quartz  of  the  fine 
muscovite  intergrowTths.  No  plate  mica  occurs,  and  the  only  possible 
utilization  of  the  mineral  is  as  scrap  mica. 

Biotite  is  abundant,  though  much  less  so  than  the  muscovite.  It 
occurs  in  small  lath-shaped  crystals,  oriented  in  every  direction  in  the 
pegmatite  mass.  A few  are  a foot  long  and  2 inches  wide,  but  the 
majority  do  not  average  more  than  2 inches  long  and  1 inch  in  width. 
A central  “ stalk’ ’ of  biotite  with  smaller  lath-shaped  crystals  radiating 
from  it  is  not  uncommon. 

Lepidolite  is  abundant  near  the  pockets  in  irregular  aggregates  of 
small  plates  or  prisms  one-sixteenth  to  one-eighth  of  an  inch  across, 
and  in  larger  more  or  less  curved  crystals.  In  many  places  it  forms 
narrow  borders  about  hexagonal  muscovite  plates,  the  two  varieties 
of  mica  being  crystallographically  continuous.  Mr.  Wade  reports  one 


58  PEGMATITES  AND  ASSOCIATED  ROCKS  OF  MAINE. 

diamond-shaped  book  of  muscovite  a foot  across  with  a border  zone 
of  lepidolite  4 inches  wide.  As  in  the  other  Maine  quarries  in  which 
gem  tourmalines  occur,  the  presence  of  the  lithium  mica  is  considered 
a favorable  indication  of  the  near  presence  of  gem-bearing  pockets. 

Black  tourmaline,  as  already  stated,  occurs  in  the  pocket-bearing 
zone  of  the  pegmatite  above  the  garnetiferous  layers.  It  is  never 
found  in  the  pockets,  where  all  the  tourmalines  are  colored  either 
pink,  blue  green,  or  occasionally  emerald  green.  Most  pockets  con- 
tain tourmalines  of  only  a single  color,  but  in  some  both  pink  and 
green  varieties  are  found,  and,  indeed,  the  two  colors  frequently  occur 
in  the  same  crystal.  Colored  tourmalines,  most  of  them  partly  or 
wholly  opaque,  also  occur  in  the  solid  pegmatite  near  the  pockets  in 
association  with  lepidolite,  clevelandite,  and  quartz,  and  some  of  these 
crystals  are  curved  through  angles  as  great  as  60°  or  even  90°.  Green 
tourmalines  also  occur  intergrown  parallel  to  the  plates  in  the  musco- 
vite books. 

The  hydromica  cookeite  occurs  principally  in  the  pockets  with 
quartz  as  a coating  on  lepidolite,  quartz,  feldspar,  and  tourmaline. 

The  tourmalines,  lepidolite,  and  clevelandite  are  beyond  doubt 
crystallizations  from  the  original  pegmatite  magma.  The  cookeite, 
purple  apatite  crystals,  and  certain  opaque  white  outer  coatings  of 
quartz  on  the  clearer  crystals  of  gray  quartz,  are  believed  to  be  later 
crystallizations  from  gaseous  or  aqueous  solutions. 

All  of  the  pockets  thus  far  encountered  in  this  pegmatite  have 
been  in  the  portion  lying  above  the  garnetiferous  bands.  The  portion 
below  it  seems  to  be  wholly  devoid  of  pockets  and  hence  of  gem 
minerals.  No  pockets  were  exposed  at  the  time  of  the  writer’s  visit, 
but  those  which  have  been  encountered  are  said  to  range  from  a few 
inches  to  several  feet  in  diameter.  Though  occurring  apparently 
only  within  a nearly  flat-lying  pocket-bearing  zone  their  horizontal 
distribution  seems  to  be  totally  irregular.  Their  walls  usually  con- 
sist mainly  of  clevelandite,  lepidolite,  and  quartz,  but  have  in  most 
cases  been  much  weathered  and  shattered  by  frost. 

The  early  excavations  at  the  original  Pulsifer  pit  disclosed  a number 
of  pockets  containing  beautiful  and  very  perfect  crystals  of  purple 
apatite.  The  form  of  these  crystals  and  their  mode  of  occurrence 
have  been  described  by  Wolff  and  Palache;0  most  of  them  are  now 
in  the  mineralogical  museum  of  Harvard  College.  The  largest 
pocket  yielded  over  2 pounds  of  loose  crystals  and  a dozen  large 
groups  of  crystals  in  the  matrix.  Most  of  them  occurred  on  or 
embedded  in  layers  of  the  opaque  white  quartz  which  coat  many  of 
the  crystals  of  transparent  quartz  in  the  pockets. 

The  distribution  of  the  cavities  is  exceedingly  irregular,  and  no 
prediction  can  be  made  as  to  the  success  which  will  attend  further 


a Wolff,  J.  E.,  and  Palache,  C.,  Apatite  from  Minot  [should  be  Auburn],  Me.:  Proc.  Am.  Acad.  Arts 
and  Sci.,  vol.  37,  No.  18,  1902,  p.  515. 


ANDROSCOGGIN  COUNTY. 


59 


mining.  The  relations  shown  in  the  present  pit  seem  to  indicate 
that  the  trend  of  the  garnetiferous  layer  above  described  may  be 
taken  as  an  indicator  of  the  trend  of  the  pocket-bearing  portion 
lying  just  above  it.  Further  excavation  in  this  zone  is  fairly  certain 
to  disclose  gem-bearing  pockets,  but  excavation  below  the  garnet- 
bearing layer  has  not  been  fruitful.  Great  care  should  be  used  in 
drilling  and  blasting,  for  injudicious  placing  of  the  drill  holes  and 
heavy  blasting  with  dynamite  are  likely  to  shatter  valuable  material. 

The  pegmatite  at  this  locality  is  cut  by  a dike,  2\  feet  wide,  of 
fine-grained  altered  diabase. 

The  precise  value  of  the  gems  and  museum  specimens  taken  from 
this  locality  can  not  be  determined,  but  so  far  as  known  to  the 
writer,  no  gems  of  over  6 or  8 carats  have  been  obtained.  Mr. 
Pulsifer  estimates  the  value  of  the  materials  taken  from  the  pit 
operated  by  him  at  about  $2,000. 

MINOT. 

In  the  southeastern  part  of  the  town  of  Minot,  near  the  Auburn 
line,  some  pegmatite  which  appears  to  be  of  commercial  grade  occurs 
on  the  farm  of  Edward  Hackett,  where  masses  of  practically  pure 
feldspar,  2 J to  3 feet  across,  are  associated  with  masses  of  pure  quartz 
of  similar  dimensions.  Almost  no  biotite,  garnet,  or  black  tourmaline 
was  seen.  The  pegmatite  seems  to  underlie  a mass  of  finely  pegmatitic 
granite.  There  is  no  doubt  of  its  commercial  quality,  but  as  the 
present  outcrops  cover  an  area  only  about  100  feet  or  so  square,  it 
is  uncertain  whether  the  quantity  would  warrant  mining.  The 
locality  is,  however,  worth  prospecting. 

POLAND. 

A quarry  located  just  across  Androscoggin  River  from  Mount 
Apatite,  about  3 miles  from  Littlefield  station,  on  the  Lewiston 
branch  of  the  Grand  Trunk  Railway,  in  the  town  of  Poland,  is 
operated  for  feldspar  and  occasional  gem  minerals  by  A.  R.  Berry, 
R.  D.  No.  7,  Auburn,  Maine. 

The  quarry  was  opened  in  1900  and  has  been  worked  intermittently 
on  a small  scale  ever  since.  It  was  visited  by  the  writer  in  August, 
1906.  The  openings,  which  are  very  irregular  and  cover  an  area 
of  about  2 acres,  are  shallow  open  pits,  none  of  them  more  than  18 
or  20  feet  in  maximum  depth. 

The  general  character  of  the  pegmatite  is  similar  to  that  at  the 
Maine  Feldspar  Company’s  quarries  at  Mount  Apatite.  The  rock 
is  mainly  a graphic  intergrowth  of  quartz  with  buff-colored  microcline 
and  some  orthoclase.  Some  albite  in  irregular  crystals  a few  inches 
across  is  encountered.  • 

Muscovite  occurs,  as  at  the  Wade  and  Pulsifer  quarries,  in  brush- 
like and . rosette-like  intergrowths  with  quartz.  No  plate  mica 


60 


PEGMATITES  AND  ASSOCIATED  EOCKS  OF  MAINE. 


occurs,  and  no  attempt  has  been  made  to  market  the  material  as 
scrap  mica. 

Biotite  is  locally  very  abundant,  occurring  as  irregularly  disposed 
blades  or  bundle-like  masses  in  which  thin  layers  of  feldspar  or 
quartz  occur  between  the  blades.  Such  biotitic  bundles  occur  in 
association  with  the  coarser  phases  of  the  pegmatite,  and  render 
valueless  for  pottery  purposes  much  feldspar  which  could  otherwise 
be  used. 

The  lithium  mica,  lepidolite,  occurs  in  the  pockets  and  near  them 
in  the  usual  forms,  similar  to  those  described  from  the  Wade  and 
Pulsifer  quarries.  (See  pp.  57-58.) 

Black  tourmaline  is  abundant  in  certain  parts  of  the  pegmatite, 
usually  in  intergrowth  with  quartz,  one  mass  of  intergrown  quartz 
and  black  tourmaline  being  10  to  12  inches  across.  One  black 
tourmaline  crystal  observed  was  5 by  12  inches  in  size.  In  the  pockets 
no  black  tourmaline  is  found,  but  some  emerald-green,  blue-green, 
and  pink  transparent  varieties  occur,  usually  embedded  in  a mass  of 
kaolin,  cookeite,  etc.,  at  the  bottoms  of  the  pockets.  The  largest 
colored  tourmaline  obtained  at  this  quarry  was  a pale-green  crystal 
about  1J  inches  in  diameter.  Only  an  inch  of  the  base  was  found 
and  it  was  too  much  flawed  to  cut  any  gems.  Many  of  the  smaller, 
colored  tourmalines  are  hollow  and  can  be  strung  like  beads.®  Slender 
flattened  prisms  of  opaque  to  transparent  green  tourmaline  occur, 
penetrating  and  interleaved  with  muscovite  plates. 

A few  fine  crystals  of  purple  apatite  similar  to  those  found  at  the 
Wade  and  Pulsifer  quarries  have  been  obtained  from  some  pockets. 
In  some  of  the  finer-grained  portions  of  the  pegmatite  the  writer 
observed  numerous  small  vugs,  rarely  more  than  a cubic  centimeter 
or  two  in  volume.  These  were  generally  surrounded  by  albite  in 
small  bladelike  crystals.  Attached  to  or  embedded  in  the  albite  at 
their  base  or  along  their  flanks,  but  otherwise  free,  occur  hexagonal 
prisms,  from  one-sixteenth  to  one-fourth  inch  in  diameter,  of  pale 
greenish  blue  to  pale  lavender  apatite.  These  plainly  were  among 
the  last  of  the  pegmatite  constituents  to  crystallize,  being  in  part  con- 
temporaneous with  the  albite  and  in  part  later.  Blue-gray  apatite 
in  flat,  bladelike  prisms  one-fourth  to  one-half  inch  across  also 
occurs.  Beryl  and  amblygonite  occur  as  constituents  of  the  solid 
pegmatite,  as  in  most  of  the  pegmatites  bearing  gem  tourmaline. 
Herderite  in  crystals  up  to  one-half  inch  in  length  is  found  in  some 
pockets. 

The  distribution  of  pockets  at  this  quarry  is  very  irregular,  and  the 
writer  saw  no  structures  which  indicated  even  in  a general  way 
the  attitude  of  the  deposit.  There  is  unquestionably  a considerable 


a In  the  summer  of  1910,  since  the  above  account  was  written,  several  pockets  containing  fine  gem 
tourmalines  were  discovered  by  Mr.  F.  S.  Havey  in  the  western  part  of  the  quarry  near  a diabase  dike. 
Mr.  Havey  was  working  the  quarry  for  feldspar  for  the  Maine  Feldspar  Company. 


CUMBERLAND  COUNTY. 


61 


amount  of  commercial  feldspar  of  pottery  grade  still  available  at  the 
locality. 

The  feldspar  is  excavated  by  hand  drilling  and  blasting,  and  after 
hand  sorting  is  hauled  by  wagons  3 miles  to  Littlefield  station,  where 
it  is  sold  to  the  Maine  Feldspar  Company  and  ground  at  that  com- 
pany’s mill.  Gem  tourmalines  and  minerals  of  value  as  cabinet 
specimens  are  not  encountered  so  frequently  that  it  is  profitable  to 
work  the  deposit  for  them  alone.  In  1906  the  quarry  force  con- 
sisted of  three  men.  The  gems  and  other  valuable  minerals  obtained 
are  marketed  irregularly  through  local  collectors,  and  no  estimate 
of  their  value  is  obtainable.  The  feldspar  output  is  a few  hundred 
tons  a year. 

CUMBERLAND  COUNTY. 

BRUNSWICK. 

The  relations  between  the  granite  and  pegmatite  in  the  town  of 
Brunswick  is  well  shown  at  the  Woodside  quarry,  about  miles 
southeast  of  Hillside  station.  This  is  an  old  quarry,  where  granite 
for  flagging  and  underpinning  has  been  obtained.  The  sheeting  of 
the  granite  here  is  very  perfect  and  nearly  horizontal. 

On  the  south  wall  of  this  quarry  much  pegmatite  is  associated  with 
the  granite.  Many  of  the  pegmatite  masses  of  lenticular  or  ex- 
tremely irregular  form  grade  into  the  granite  in  the  most  gradual  and 
complete  manner  and  are  characterized  by  identical  minerals.  They 
differ  from  the  granite  only  in  texture,  and  there  can  be  no  question 
that  the  two  rocks  solidified  practically  contemporaneously  from  the 
same  magma.  Other  pegmatite  dikes,  however,  distinctly  cut  the 
granite  with  sharp  contacts.  The  entire  mineralogic  similarity  of 
this  second  type  to  the  pegmatite  which  grades  into  the  granite  leads 
to  the  belief  that  the  two  types  are  genetically  connected  and  that  the 
intrusion  of  the  pegmatite  masses  that  show  sharp  boundaries  fol- 
lowed quickly  on  the  solidification  of  the  granite  which  they  cut. 

Very  similar  relations  were  observed  at  the  Grant  quarry,  about 
lb  miles  east  of  Hillside  and  3 miles  west  of  Brunswick.  This  quarry 
has  been  described  by  Dale.® 

The  relations  between  the  pegmatite  and  foliated  rocks,  which  are 
probably  of  igneous  origin,  is  well  exhibited  in  Brunswick  village  at  a 
quarry  for  road  materials  near  the  Lewiston  branch  of  the  Maine 
Central  Railroad.  The  folia  in  the  rocks  are  in  many  places  very 
straight  and  regular  for  considerable  distances.  Much  of  the  rock 
is  a light-gray  schist  which  has  the  mineral  composition  of  a horn- 
blende granite. 

The  slide  of  this  rock  examined  shows  an  interlocking  granular 
texture  in  which  most  of  the  grains  range  from  0.15  to  0.60  milli- 


« Dale,  T.  N.,  The  granites  of  Maine:  Bull.  U.  S.  Geol.  Survey  No.  313, 1907,  p.  76. 


62 


PEGMATITES  AND  ASSOCIATED  ROCKS  OF  MAINE. 


meter.  It  is  composed  of  about  two-fifths  quartz,  two-fifths  feld- 
spar, and  one-fifth  hornblende,  with  subordinate  titanite  and  biotite. 
Some  of  the  hornblende  crystals  are  1.2  millimeters  in  length.  Their 
tendency  to  parallel  elongation  and  to  greater  abundance  in  some 
layers  than  in  others  gives  the  rock  its  schistose  character.  Biotite 
is  also  most  abundant  in  the  layers  that  are  most  hornblendic.  The 
feldspar  is  principally  orthoclase  with  a little  microcline  and  plagio- 
clase  near  andesine.  Many  of  the  quartz  grains  show  strain  shadows, 
but  there  is  no  other  evidence  of  dynamic  action. 

Alternating  with  this  rock  are  bands  of  very  dark  gray  to  nearly 
black  hornblende-biotite  schist  with  lustrous  cleavage  faces.  An 
intermediate  phase  is  a dark-gray  hornblende  schist  with  a few  narrow 
quartz  bands  up  to  about  one-eighth  inch  across. 

Under  the  microscope  this  rock  is  seen  to  consist  of  quartz,  plagio- 
clase,  and  hornblende.  The  plagioclase  is  andesine  and  is  about 
equal  to  hornblende  in  abundance.  Quartz  is  slightly  less  abundant 
than  either.  Titanite  is  subordinate.  Occasional  narrow  bands  are 
more  coarsely  crystalline  and  are  largely  quartz,  with  some  feldspar. 
Their  grains  interlock  intimately  with  those  of  the  finer  portions  of 
the  rock.  The  schistosity,  as  in  the  more  acidic  bands,  is  due  to  the 
concentration  of  hornblende  along  certain  planes  and  of  quartz  along 
certain  others  and  to  parallel  elongation  of  many  of  the  hornblende 
crystals. 

If  these  schists  represent  original  sediments  their  recrystallization 
has  been  so  complete  as  to  obliterate  all  traces  of  such  an  origin. 
The  abundance  of  feldspar,  on  the  other  hand,  especially  in  the  more 
basic  bands,  renders  it  much  more  probable  that  they  are  primary 
or  flow  schists. 

The  pegmatite  in  some  cases  is  in  sharp  contact  with  the  gneiss,  and 
the  contacts  may  parallel  or  cut  across  the  foliation.  In  other  cases 
the  pegmatite  seems  to  grade  into  the  gneiss  with  such  completeness 
as  to  indicate  either  that  portions  of  the  gneiss  were  not  yet  com- 
pletely solidified  when  the  pegmatite  was  intruded  or  that  the  peg- 
matite produced  locally  very  complete  recrystallization  in  the  schist. 
The  pegmatite  is  a typical  biotite  pegmatite  showing  much  graphic 
granite  and  a few  crystals  of  pure  feldspar  4 or  5 inches  across. 

WESTBROOK. 

A quartz  deposit  which  was  worked  to  a small  extent  many  years 
ago  is  located  about  1 mile  northwest  of  the  village  of  Cumberland 
Mills.  The  quartz  forms  part  of  a pegmatite  dike  intruding  mica 
schist  and  granodiorite.  The  width  of  the  dike  varies  from  2 to 
10  feet,  and  its  trend  is  nearly  north  and  south.  Most  of  the  mass 
is  typical  granite-pegmatite  of  moderate  coarseness,  but  with  this 
is  associated  a body  of  nearly  pure  white  quartz,  which  in  places 


HANCOCK  COUNTY. 


63 


seems  intrusive  in  the  pegmatite,  though  elsewhere  passing  gradually 
into  it.  The  quartz  quarried  was  taken  to  Portland  and  there  ground 
for  use  in  pottery  and  filters. 

HANCOCK  COUNTY. 

Pegmatite  is  present  only  in  relatively  minor  amounts  in  association 
with  the  granites  of  Hancock  County.  The  occurrence  of  molybdenite 
with  pegmatite  at  Catherine  Hill,  near  Tunk  Pond,  has  been  described 
by  Emmons. a 

LINCOLN  COUNTY. 

EDGECOMB. 

The  rocks  of  the  town  of  Edgecomb  are  mainly  quartz-mica  schists 
of  sedimentary  origin  which  have  been  intruded  by  pegmatite,  granite, 
and  minor  amounts  of  granite  gneiss.  The  pegmatites  have  been 
exploited  for  feldspar  at  one  locality  near  the  center  of  the  town. 

Edgecomb  feldspar  quarry. — A feldspar  quarry,  long  since  aban- 
doned, is  situated  2\  miles  south  of  the  village  of  Newcastle  and 
about  one-half  mile  south  of  the  road  extending  from  North  Edge- 
comb to  Briar  Cove,  on  Damariscotta  River.  It  is  within  the  Booth- 
bay  quadrangle  of  the  United  States  Geological  Survey. 

The  locality  was  visited  by  the  writer  in  August,  1906.  The 
excavations  consist  of  two  open  pits,  one  150  feet  long  and  50  feet 
wide,  filled  with  water  at  the  time  of  the  writer’s  visit;  the  other 
50  feet  long,  25  feet  wide,  and  15  feet  deep.  The  soil  overburden  is 
slight.  The  pegmatite  resembles  in  its  mineral  character  that  quar- 
ried at  Topsham,  in  Sagadahoc  County,  but  contains  less  feldspar  of 
commercial  grade. 

The  quartz  is  not  abundant  enough  to  be  of  commercial  importance. 
The  largest  masses  observed  are  between  the  two  pits  and  are  3 feet 
across.  The  color  varies  from  white  to  dark  gray. 

The  feldspar  is  buff  to  cream-colored  orthoclase  and  microcline, 
occurring  principally  in  graphic  intergrowth  with  quartz.  At  the 
northwest  end  of  the  larger  pit  some  masses  of  nearly  pure  feldspar 
are  3 feet  across,  but  such  size  is  quite  exceptional. 

Biotite  in  the  usual  lath-shaped  crystals,  in  places  attaining  a 
length  of  3 feet,  is  very  abundant  and  is  the  most  injurious  of  the 
mineral  constituents,  black  tourmaline  being  wholly  absent  so  far 
as  observed. 

Pink  opaque  garnets  occur  locally  but  are  not  abundant.  Many  of 
them  are  inclosed  by  muscovite. 

As  far  as  could  be  observed,  very  little  feldspar  of  a quality  suitable 
for  the  pottery  trade  remains  at  this  locality,  the  prevalence  of 


a Emmons,  W.  H.,  Ore  deposits  of  Maine  and  the  Milan  mine,  New  Hampshire:  Bull.  U.  S.  Geol.  Survey 
No.  432,  1910,  p.  42. 


64 


PEGMATITES  AND  ASSOCIATED  EOCKS  OF  MAINE. 


biotite  rendering  most  of  the  material  worthless  for  that  purpose. 
The  water  in  the  larger  pit  of  course  prevented  its  thorough  exami- 
nation. An  examination  of  the  vicinity  yielded  no  information  as 
to  the  trend  or  extent  of  the  deposit,  and  showed  no  other  masses  of 
commercially  valuable  feldspar.  No  gem  minerals  have  been 
reported,  and  there  are  no  indications,  such  as  the  occurrence  of 
pockets,  lepidolite,  black  tourmaline,  etc.,  that  any  are  likely  to  be 
found.  Under  present  commercial  conditions,  the  deposit  may  be 
regarded  as  worked  out.  It  may  in  the  future  be  of  value  if  some 
commercially  practical  method  of  separating  the  mica  can  be  devised, 
or  it  may  be  used  for  purposes  where  the  presence  of  black  mica 
(biotite)  is  not  detrimental,  such  as  for  fertilizing,  poultry  grit,  ready 
roofing,  etc. 

Geologic  relations. — About  half  a mile  north  of  the  Edgecomb 
feldspar  quarry,  on  the  north  side  of  the  road,  the  predominant 
rock  is  a medium-grained  granite  of  slightly  varying  texture,  which 
along  certain  bands  and  in  some  irregular  patches  is  pegmatitic. 
The  constituents  of  the  granite  are  identical  with  those  of  the  peg- 
matite and  there  can  be  no  question  that  the  two  rocks  solidified 
from  the  same  parent  magma  at  about  the  same  time.  Muscovite 
is  almost  entirely  absent  from  this  granite,  as  it  is  from  the  pegmatite 
of  the  above-described  feldspar  quarry,  biotite  being  the  dominant 
mica.  West  of  these  granite  outcrops  extensive  ledges  of  pegmatite 
intrude  quartz-mica  schists  in  a very  irregular  manner,  at  many  places 
cutting  sharply  across  their  foliation. 

Typical  structural  relations  between  the  pegmatite  and  the  schists 
are  well  shown  along  the  north  shore  of  the  narrow  gurnet  known 
as  the  Oven  Mouth.  Here  the  schists  are  traversed  by  numerous 
small  pegmatite  intrusions,  most  of  which  are  parallel  to  the  schist 
folia  or  cut  them  at  low  angles  only. 

The  smaller  pegmatite  intrusions  commonly  assume  the  form. of 
a series  of  connecting  lenticles  or  show  periodic  swellings  along 
their  lengths.  The  schists  are  dark  gray  to  purplish  and  show  quartz, 
biotite,  and  hornblende  as  their  dominant  constituents,  with  mus- 
covite and  garnet  as  accessories.  Feldspar  was  not  observed  and  if 
present  at  all  is  very  meager  in  amount.  The  schists  are  almost 
certainly  of  sedimentary  origin. 

BOOTHBAY  HARBOR. 

Character  and  relations  of  the  pegmatite. — The  rocks  of  the  town  of 
Boothbay  Harbor  are  largely  quartz-mica  schists  which  are  intruded 
and  in  many  places  intimately  injected  by  granite  and  pegmatite. 
Two  occurrences  of  the  very  unusual  rock  prowersose  were  also 
observed.  Very  excellent  and  instructive  exposures  occur  along  the 
irregular  shore  line  of  this  region,  and  although  none  of  the  peg- 


LINCOLN  COUNTY.  65 

matites  have  proved  commercially  valuable  their  geologic  relations 
at  a number  of  points  are  of  much  scientific  interest. 

Excellent  exposures  on  the  first  point  west  of  Boothbay  Harbor 
village  show  the  intrusive  pegmatite  and  the  intruded  quartz-biotite 
schists  locally  very  much  contorted,  much  as  if  the  two  had  been 
stirred  up  together  with  a gigantic  spoon.  In  most  places,  however, 
the  schist  is  of  fairly  uniform  trend  over  considerable  areas.  Other 
exposures  just  west  of  these  show  a number  of  schist  fragments 
inclosed  by  the  pegmatite.  The  fragments  are  sub  angular,  but  at 
their  extremities  tail  out  somewhat  into  the  pegmatite.  The  frag- 
ments as  a whole  appear  therefore  to  have  maintained  their  rigidity 
but  to  have  yielded  somewhat  about  their  borders  to  the  deforming 
action  of  the  intrusive  pegmatite. 

On  the  shore  of  McKown  Point  about  one-fourth  mile  south  of 
the  United  States  fish  hatcheries  pegmatite  and  granite  are  intrusive 
into  quartz-mica  schists.  The  contact  between  the  schist  and  the 
igneous  rocks  is  sharp,  neither  rock  showing  any  notable  changes  in 
grain  or  texture  as  the  contact  is  approached.  The  transition  from 
pegmatite  to  granite  is  also  abrupt,  although  crystallographic  con- 
tinuity is  preserved.  It  is  impossible  to  say  which  is  the  intruded 
and  which  the  intrusive  rock,  and  their  association  is  extremely 
irregular.  The  granite  shows  distinct  flow  lines  parallel  in  a general 
way  to  the  schist  walls  and  particularly  well  developed  next  the 
pegmatite.  The  latter  also  shows  a tendency  toward  the  develop- 
ment of  faint  flow  lines  next  the  granite,  these  being  defined  by  a 
concentration  of  biotite  plates  along  certain  planes. 

The  granite  gneiss  is  dark  buff  to  gray  and  shows  a rather  faint 
foliation  due  to  the  aggregation  of  the  biotite  along  certain  planes 
or  lenses  few  of  which  are  continuous  for  more  than  one-half  or 
three-fourths  of  an  inch.  The  interspaces  are  largely  quartz  and 
feldspar.  Under  the  microscope  the  mineral  constituents  in  order 
of  abundance  are  seen  to  be  quartz  > orthoclase  and  microcline  > or 
= oligoclase  > biotite  > muscovite.  Orthoclase  is  greatly  in  excess 
of  microcline  and  occurs  in  larger  grains.  The  average  size  of  grain 
is  about  1 millimeter,  though  a few  feldspars  are  2 millimeters  across. 
The  rock  is  very  fresh,  though  some  of  the  feldspars  show  a slight 
clouding  with  decomposition  products.  No  parallel  structure  is 
observable  under  the  microscope.  There  is  complete  interlocking  of 
the  grains,  which  show  no  important  amount  of  fracturing,  no 
crushed  borders,  nor  any  other  evidence  of  dynamic  action.  The 
foliation  appears  to  be  an  original  feature  developed  by  flowage 
before  complete  solidification. 

The  pegmatite  associated  with  the  gneiss  shows  light-gray  quartz 
and  gray  to  buff  feldspars  in  nearly  equal  amounts,  with  biotite  the 
63096°— Bull.  445—11 5 


66 


PEGMATITES  AND  ASSOCIATED  ROCKS  OF  MAINE. 


dominant  mica,  as  in  the  gneissic  granite.  The  texture  is  wholly 
irregular  and  typically  pegmatitic  because  of  the  great  range  in  size 
exhibited  by  crystal  grains  of  the  same  mineral  species.  Quartz 
is  the  most  abundant  mineral  with  microcline  >oligoclase  >biotite 
> or  = orthoclase  > muscovite.  The  rock  differs  from  the  associated 
gneissic  granite  mainly  in  its  texture  and  in  the  fact  that  microcline 
dominates  over  orthoclase  instead  of  bearing  the  reverse  relation  to  it. 

The  close  association  of  the  granite  and  pegmatite  and  the  fact 
that  the  same  minerals  are  present  in  the  same  order  of  abundance 
in  both  rocks  is  highly  suggestive  of  a genetic  connection  between  the 
two. 

At  a point  on  the  east  shore  of  Boothbay  Harbor  the  fine-grained 
pegmatite  was  observed  to  be  traversed  by  a vein  of  white  quartz 
2 to  3 inches  in  width.  The  borders  of  this  vein  are  not  sharp; 
feldspar  crystals  of  the  bordering  pegmatite  project  into  it,  and  in 
some  instances  their  inner  borders  (next  the  quartz)  show  well- 
developed  crystal  faces.  Isolated  crystals  of  feldspar  up  to  3 inches 
in  length  also  occur,  apparently  wholly  surrounded  by  the  quartz  of 
the  vein.  The  feldspathic  character  of  this  vein  and  the  absence  of 
a sharp  or  straight  boundary  between  it  and  the  pegmatite  indicate 
that  it  was  not  deposited  as  a fissure  filling  along  a fracture  plane  trav- 
ersing solid  pegmatite,  but  rather  that  it  was  genetically  a part  of  the 
pegmatite  magma  and  was  formed  before  the  complete  solidification 
of  its  host.  Apparently  it  represents  an  end  product  of  the  pegmatite 
crystallization.  The  sheetlike  form  of  the  vein  indicates  presumably 
that  the  pegmatite  was  sufficiently  rigid  to  permit  the  formation  of 
a rift  of  some  sort  along  which  the  more  quartzose  magma  could 
penetrate,  but  that  coarsely  interlocking  crystallization  between 
vein  and  wall  was  still  possible.  Similar  relationships  have  been 
observed  by  the  writer  on  a larger  scale  in  some  of  the  feldspar  quar- 
ries of  Connecticut.  (See  PL  XVI,  B,  p.  18.)  They  are  of  impor- 
tance as  showing  without  much  question  that  many  at  least  of  the 
quartz  veins  associated  with  the  pegmatites  may  be  regarded  as  an 
end  product  of  the  crystallization  of  the  pegmatite  magma. 

Southward  along  the  east  shore  of  Boothbay  Harbor  to  Spruce 
Point  abundant  dikes  of  pegmatite  are  found  traversing  the  schists; 
they  vary  from  one-fourth  to  one-half  an  inch  to  10  feet  or  even  50 
feet  across.  Nearly  all  of  the  dikes  and  particularly  the  smaller 
ones  assume  the  form  of  a succession  of  connecting  lenses,  indicating 
a very  uneven  penetration  of  the  pegmatite  magma  between  the 
schist  folia.  The  schists  usually  exhibit  a thickening  of  their  laminae 
opposite  the  “nodes”  of  these  irregularly  bulging  dikes,  indicating  a 
crystallographic  rearrangement  of  the  schist  constituents  as  an 
accompaniment  of  the  pegmatite  intrusion. 


LINCOLN  COUNTY. 


67 


It  is  significant  that  numerous  dikes  of  granite  also  exposed  along 
this  shore  never  exhibit  such  irregular  swelling  and  thinning,  but  are 
nearly  parallel- walled  even  where  intruded  parallel  to  the  foliation 
of  the  bordering  schists. 

On  the  point  due  north  of  Cabbage  Island  the  rocks  are  almost 
entirely  granite  and  pegmatite  associated  in  a very  irregular  mann'er. 
The  pegmatite  forms  dikes  of  varying  width  and  irregular  boundaries 
in  the  granite  and  also  forms  narrow  stringers  and  wholly  irregular 
patches.  In  general  the  change  from  *one  rock  to  the  other  is  rather 
abrupt,  although  characterized  by  complete  crystallographic  conti- 
nuity. In  the  places  where  the  association  is  most  intimate  and 
irregular  it  is  difficult  to  see  how  the  granite  could  have  been  wholly 
solidified  at  the  time  of  the  pegmatite  crystallization. 

The  granite  is  gray  to  pinkish,  with  a faint  local  foliation.  The 
average  size  of  grains  is  about  one-half  to  three-fourths  of  a millimeter. 
The  texture  is  typically  granitic  with  quartz  > orthoclase  and  micro- 
cline  > oligoclase  > biotite  > muscovite.  The  quartz  shows  undulatory 
extinctions.  Some  of  the  smaller  quartz  crystals  are  inclosed  by 
orthoclase  or  oligoclase  and  show  rounded  outlines.  Some  of  the 
quartz  also  crystallized  earlier  than  or  contemporaneously  with  the 
biotite  crystallization.  The  bulk  of  the  quartz,  characterized  by 
more  irregular  outlines  and  larger  grains,  is  a later  crystallization 
than  the  biotite  and  appears  to  be  about  contemporaneous  with  the 
feldspars.  Among  the  feldspars  orthoclase  is  present  in  greater 
abundance  and  larger  grains  than  microcline.  Oligoclase  is  almost 
equal  to  the  potash  feldspar  in  abundance.  Many  of  the  feldspar 
crystals  inclose  small  crystals  of  muscovite,  which  are  apparently 
original.  Some  micrographic  intergrowths  of  feldspar  and  quartz 
occur. 

The  pegmatite  is  characterized  by  the  same  minerals  as  the  granite. 
Quartz  is  the  dominant  constituent,  with  orthoclase  and  microcline 
second  and  oligoclase  third.  Biotite  dominates  over  muscovite,  but 
is  less  abundant  than  in  the  granite.  The  quartz  exhibits  little  or 
no  undulatory  extinction.  Some  of  the  grains  exhibit  crystal  out- 
lines on  certain  sides,  but  the  outlines  of  others  are  very  irregular. 
The  feldspars  exhibit  only  slight  decomposition. 

It  is  notable  that  both  rocks  carry  the  same  minerals  in  the  same 
order  of  abundance. 

In  general  the  pegmatite  characteristic  of  the  Boothbay  Harbor 
region  shows  considerable  uniformity  in . mineralogical  make-up. 
Characteristically  it  shows  irregular  crystals  of  orthoclase-microcline, 
ranging  in  diameter  up  to  6 inches,  surrounded  by  a less  coarsely 
crystalline  association  of  potash  feldspar,  white  to  gray  or  amber- 
colored  quartz  in  masses  sometimes  several  inches  across,  small 
amounts  of  nearlv  white  plagioclase,  and  varying  proportions  of 


68 


PEGMATITES  AND  ASSOCIATED  ROCKS  OF  MAINE. 


muscovite  and  biotite  in  crystals  seldom  over  an  inch  across,  usually 
more  or  less  aggregated  in  bunches.  Red  garnets  are  present  in 
varying  but  small  numbers  and  are  rarely  over  one-fourth  inch  in 
diameter.  Small  amounts  of  a white  sugary  matrix  are  not  uncom- 
mon and  consist  largely  of  a fine  graphic  intergrowth  of  quartz  and 
feldspar. 

Schist  associated  with  'pegmatites . — A specimen  of  schist  collected 
along  the  shore  near  the  United  States  fish  hatcheries  on  McKown 
Point  illustrates  the  indeterminate  character  of  some  of  the  foliates 
associated  with  the  pegmatite.  The  rock  is  dark-gray,  millimeter 
grained,  with  a fairly  perfect  foliation  due  mainly  to  parallel  orienta- 
tion of  the  mineral  grains  but  accentuated  by  quartz  laminse  1 to  2 
millimeters  across. 

Under  the  microscope  the  texture  is  seen  to  be  interlocking 
granular,  the  constituents  being  quartz  > hornblende  > labradorite, 
with  biotite,  titanite,  calcite,  and  apatite  subordinate.  Mineral- 
ogically  the  rock  is  therefore  a quartz-rich  diorite.  Many  of  the 
quartzes  extinguish  abruptly,  though  some  show  slight  undulatory 
extinction.  The  green  hornblende  grains  are  very  irregular,  but* 
show  a tendency  towards  elongation  in  a parallel  direction.  This 
elongate  character,  together  with  the  tendency  toward  aggregation 
of  the  quartz  grains  along  certain  lines,  produces  the  foliated  struc- 
ture. Titanite  is  very  abundant  in  irregular  grains  and  also  in 
grains  showing  elongate  rhombic  outlines.  The  hornblende  shows 
no  alteration  whatever.  The  feldspar  is  in  part  perfectly  fresh  but 
some  of  the  grains  show  saussuritization. 

Calcite,  which  is  present  in  moderate  amounts,  is  in  contact  with 
quartz,  titanite,  or  unaltered  feldspar  or  hornblende,  the  contacts 
being  as  sharp  as  between  any  others  of  the  rock  constituents.  Its 
abundance  is  scarcely  explainable  by  the  very  slight  alteration 
characteristic  of  most  of  the  rock,  and  it  is  necessary  to  assume 
either  that  it  completely  replaced  certain  grains  or  portions  of  grains 
of  other  minerals,  without  any  of  the  mottling  and  irregular  pene- 
tration usually  characteristic  of  such  replacement,  or  else  to  assume 
that  it  crystallized  at  the  same  period  as  the  quartz,  feldspar,  horn- 
blende, etc.,  with  which  it  is  in  contact.  Such  an  association  could 
readily  be  explained  as  the  result  of  contact  or  regional  metamorphism 
of  a slightly  calcareous  arkose.  The  texture  and  mineral  composi- 
tion and  even  the  presence  of  calcite  is  not,  however,  incompatible 
with  an  igneous  rather  than  a metamorphic-sedimentary  origin. 

We  are  accustomed  to  reason  by  analogy  from  the  phenomenon 
of  calcining  observed  when  carbonates  are  heated  under  ordinary 
surface  conditions  to  the  postulate  that  carbonates,  if  they  existed 
in  igneous  rocks,  would  undergo  the  same  changes,  and  thence  to 
conclude  that  carbonates  can  not  exist  as  such  in  igneous  rocks. 


LINCOLN  COUNTY. 


69 


The  reasoning  is  obviously  weak,  because  in  the  one  case  the  con- 
ditions are  those  of  low  pressure  and  ready  escape  of  gases,  whereas 
in  the  case  of  a magma  cooling  to  form  a granular  rock  of  moderate 
coarseness  they  are  probably  those  of  relatively  high  pressure  and 
much  greater  ability  to  retain  components  which  under  surface 
conditions  would  be  freed  in  a gaseous  form.  The  microscopic 
evidence  of  the  original  character  of  the  carbonate  in  this  case  is 
regarded  as  suggestive  rather  than  conclusive,  but  there  appears  to 
be  no  a priori  reason  why  it  should  not  be  original. 

The  schist  described  lies  between  two  intrusions  of  pegmatite, 
one  5 to  6 feet  wide  and  the  other  4 to  5 feet.  The  field  and  micro- 
scopic evidence  is  insufficient  to  determine  whether  it  is  igneous  or 
metamorphic-sedimentary  in  origin,  and  because  of  the  abundance  of 
plagioclase  it  is  doubtful  whether  a chemical  analysis  would  furnish 
conclusive  evidence. 

Schists  of  the  Boothbay  Harbor  region  which  she  believes  to  be 
of  metamorphic-sedimentary  origin  have  been  described  and  analyses 
given  by  Dr.  Ida  H.  Ogilvie.® 

Syenite  porphyry. — In  1906  the  writer  described6  a rock  of  peculiar 
appearance  and  unusual  composition  from  the  town  of  Appleton  in 
Knox  County.  The  rock  is  a porphyry  showing  blue-gray  pheno- 
crysts  of  potash  feldspar  up  to  1J  inches  in  length  in  a dark-green 
groundmass  composed  mainly  of  biotite  and  hornblende  with  minor 
amounts  of  titanite,  apatite,  quartz,  magnetite,  and  albite.  Chemi- 
cally it  is  unusual  because  of  the  great  dominance  of  potash  over 
soda  in  a rock  so  femic  and  so  high  in  lime. 

Rocks  which  in  the  field  are  indistinguishable  from  prowersose 
from  the  Appleton  locality  and  which  on  chemical  analysis  fall  in 
very  closely  related  divisions  of  the  quantitative  system  of  rock 
classification,  from  several  localities  in  the  Boothbay  Harbor  region, 
have  been  described  by  Dr.  Ida  H.  Ogilvie.c 

A number  of  Dr.  Ogilvie’s  localities  were  visited  by  the  writer 
before  he  became  familiar  with  her  published  descriptions.  A 
locality  not  specifically  mentioned  by  her  is  the  shore  of  Linekin 
Bay,  southeast  of  Mount  Pisgah.  At  this  locality  and  on  Spruce 
Point  the  syenite  is  intruded  by  dikes  of  pegmatite  and  of  fine- 
grained granite.  Many  central  portions  of  the  syenite  intrusions 
show  little  or  no  foliation  and  a very  heterogeneous  orientation  of 
the  phenocrysts,  but  in  the  narrower  masses  or  near  the  borders 
of  the  larger  masses  foliation  is  well  developed,  and  is  found  to  be 
due  to  crushing  and  shearing  movements,  probably  accompanying 

a Ogilvie,  I.  H.,  A contribution  to  the  geology  of  southern  Maine:  Ann.  New  York  Acad.  Sci.,  vol.  17, 
pt.  2,  1907,  pp.  526-527. 

b Bastin,  E.  S.,  Some  unusual  rocks  from  Maine:  Jour.  Geology,  vol.  14,  1906,  pp.  173-180. 

c Ogilvie,  I.  H.,  A contribution  to  the  geology  of  southern  Maine:  Ann.  New  York  Acad.  Sci.,  vol.  17, 
pt.  2,  1907,  pp.  536-541. 


70 


PEGMATITES  AND  ASSOCIATED  ROCKS  OF  MAINE. 


dynamic  metamorphism.  On  Spruce  Point  many  of  the  feldspar 
phenocrysts  are  nearly  black  on  account  of  the  abundance  of  minute 
inclusions. 

OXFORD  COTJNTY. 

ALBANY. 

The  rocks  of  most  of  the  town  of  Albany  are  quartz-mica  schists 
of  probable  sedimentary  origin  which  have  been  intensely  injected  by 
pegmatite  and  intruded  by  dikes  of  fine-grained  granite.  In  all 
observed  places  where  the  granite  and  pegmatite  were  associated,  the 
former  was  the  older  rock.  Along  the  road  running  nearly  parallel  to 
Crooked  River,  near  the  center  of  the  town,  diorite  or  quartz  diabase 
is  of  abundant  occurrence  and  is  intruded  by  dikes  of  fine  diabase, 
fine-grained  granite  containing  few  dark-colored  minerals,  and  peg- 
matite. In  the  northwestern  part  of  the  town  a gray  granite  gneiss 
forms  the  country  rock  over  large  areas. 

French  Mountain  beryl  locality. — In  the  eastern  part  of  the  town 
of  Albany  a pegmatite  mass  very  rich  in  quartz  has  yielded  some 
beryls  of  fine  gem  quality.  The  locality  is  in  the  woods  in  a sag 
between  two  knobs  of  the  hill  crest  and  is  difficult  to  discover  without 
a guide.  Only  a few  blasts  have  been  made  in  the  ledge.  Much  of 
the  quartz  is  very  clear  and  some  is  of  a fine  rose  tint.  The  locality 
is  of  interest  to  the  mineral  collector  but  is  not  of  commercial 
importance. 

Bennett  mica  prospect. — A small  mass  of  pegmatite  which  has  been 
prospected  for  mica  by  W.  S.  Robinson  is  situated  in  the  western  part 
of  the  town  of  Albany  on  the  farm  of  F.  H.  Bennett,  about  5 miles  west 
of  Hunt  Corners.  The  pegmatite  dike  has  an  exposed  thickness  of  10 
feet  and  is  intrusive  in  granite  gneiss  similar  to  that  occurring  farther 
west.  The  pegmatite  is  a coarse  association  of  quartz,  muscovite, 
orthoclase,  and  black  tourmaline.  The  muscovite  occurs  in  graphic 
intergrowth  with  quartz  and  also  in  11  books”  up  to  6 inches  across, 
though  mostly  under  3 inches.  Nearly  all  is  of  the  wedge  variety 
and  shows  twinning.  Feldspar  is  too  intimately  mixed  with  black 
tourmaline  to  be  of  any  value.  Neither  the  quantity  nor  the  quality 
of  the  materials  here  seem  to  warrant  further  development. 

Pingree  mica  prospect. — Another  pegmatite  mass,  situated  on  the 
farm  of  C.  P.  Pingree,  in  the  extreme  western  part  of  the  town  of 
Albany,  was  worked  to  a slight  extent  for  mica  in  1878-79,  and  was 
opened  again  in  1900  by  W.  S.  Robinson;  no  shipments,  however, 
except  of  samples,  have  ever  been  made.  The  ledge  has  yielded  some 
beryls  of  gem  quality.  In  the  absence  of  the  owner  of  this  property 
the  writer  was  unable  to  visit  it.  Bethel,  the  nearest  station,  is  about 
8 miles  distant  on  the  Grand  Trunk  Railway. 


OXFORD  COUNTY. 


71 


ANDOVER. 

F.  G.  Hillman,  of  New  Bedford,  Mass.,  has  reported  his  discovery  in 
pegmatite  in  Andover  of  lilac-colored  spodumene,  or  kunzite,  as  well 
as  of  some  with  a greenish  color.  A cleavage  specimen  sent  to  the 
Survey  measured  about  12  by  10  by  3-J  millimeters  and  had  a very 
pretty  clear  pink  color.  It  was  not  entirely  without  cleavage  cracks, 
however.  The  greenish  material  was  a pale  aquamarine,  nearly 
clear,  though  rather  badly  fractured.  This  spodumene  was  obtained 
near  the  surface,  and  excavating  to  a greater  depth  has  disclosed  no 
material  of  gem  quality. 

BUCKFIELD. 

The  rocks  of  the  town  of  Buckfiekl  are  largely  quartz-mica  schists 
which  have  been  injected  by  pegmatite.  The  pegmatites  have  not 
been  extensively  worked  in  any  part  of  the  town  but  have  at  a few 
places  yielded  golden  beryl,  aquamarine,  and  caesium  beryl.  A fine 
twinned  crystal  of  chrysoberyl  from  this  town  in  the  museum  of  the 
Sheffield  Scientific  School  of  Yale  University  is  2 inches  long  and  one- 
half  inch  thick.  This  same  collection  also  contains  very  perfect 
diamond-shaped  crystals  of  muscovite  from  Buckfield. 

GREENWOOD. 

So  far  as  known  the  rocks  of  the  southern  part  of  the  town  of 
Greenwood  are  schists  which  have  been  intruded  by  granite  and 
pegmatite.  In  the  northern  part  of  the  town  granite  is  believed  to 
become  more  abundant. 

A small  abandoned  mine  which  has  yielded  many  interesting 
mineral  specimens  and  some  gem  tourmalines  is  situated  about 
three-fourths  of  a mile  east  of  Hicks  Pond  in  the  southern  part  of  the 
town.  The  pit,  which  is  15  feet  in  width  and  about  25  feet  long, 
is  located  on  the  western  slope  of  a steep  forested  hillside,  near  its 
summit.  It  was  visited  by  the  writer  in  September,  1906. 

The  rock  is  a coarse  pegmatite  made  up  largely  of  quartz,  musco- 
vite, albite  of  the  clevelandite  variety,  and  some  ortlioclase-mierocline. 
The  feldspar  does  not  occur  in  commercial  amounts.  Some  of  the 
muscovite  books  are  14  inches  across  the  plates  and  a foot  in  thick- 
ness, but  all  except  a few  show  twinning  and  wedge  structure,  which 
render  them  useless  as  a source  of  plate  mica.  In  places  mica  con- 
stitutes half  of  the  rock.  Black  tourmaline  is  present  but  is  not 
abundant. 

Pockets  are  numerous,  most  of  those  observed  being  under  1 foot  in 
diameter.  One  gigantic  one  was  7 feet  wide  and  10  feet  long,  with 
a depth  of  at  least  4 feet,  the  floor  being  buried  under  a considerable 
* thickness  of  detritus;  numerous  small  lobes  add  irregularity  to  its 


72 


PEGMATITES  AND  ASSOCIATED  ROCKS  OF  MAINE. 


form.  Wherever  the  walls  of  this  pocket  have  not  11  shelled  off”  by 
the  action  of  frost,  etc.,  they  are  covered  with  a coating  of  minute 
crystals  of  quartz.  In  some  places  the  minerals  which  have  been 
coated  in  this  way  have  subsequently  decayed,  leaving  only  their 
quartz  covering.  As  these  quartz  crystals  are  transparent  and 
usually  show  hexagonal  forms  they  probably  crystallized  below 
575°  C.,  presumably  as  a deposition  from  meteoric  waters.  Where 
this  secondary  quartz  has  been  deposited  on  original  quartz  crystals 
it  has  grown  in  perfect  crystal  continuity  with  them  but  is  distin- 
guished by  being  opaque  white  rather  than  transparent.  It  is  inter- 
esting to  note  that  this  growth  of  secondary  quartz  has  been  most 
rapid  at  the  apices  of  the  quartz  crystals,  the  coating  here  being 
much  thicker  than  on  the  sides  of  the  crystals. 

The  precise  form  and  extent  of  the  pegmatite  deposit  could  not  be 
ascertained,  but  it  appears  to  be  irregular.  The  coarse  pegmatite  is 
traceable  for  about  25  feet  north  of  the  present  pit,  beyond  which  it 
is  concealed  by  soil.  The  southern  wall  of  the  pit  is  composed  of 
schists,  which  strike  N.  50°  W.  and  dip  nearly  vertical. 

The  locality  has  yielded  a considerable  number  of  tourmalines  of 
gem  quality,  but  very  few  have  been  marketed,  much  of  the  material 
being  still  in  the  hands  of  George  Noyes,  of  Fryeburg,  who  developed 
the  property.  Other  minerals  occurring  here  are  apatite  in  small, 
opaque,  olive-green  crystals  (present  in  great  abundance  in  some  of 
the  fine-grained  parts  of  the  pegmatite),  opaque,  pale  lilac-colored 
spodumene,  cassiterite,  beryl,  herderite,a  zircon,  and  phenacite. 

The  locality,  though  affording  many  interesting  mineral  specimens, 
can  not  be  regarded  as  of  much  commercial  importance. 

HEBRON. 

The  rocks  of  the  town  of  Hebron  are  principally  quartz-mica 
schists,  extensively  intruded  and  injected  by  pegmatite,  which  shows 
great  variations  in  coarseness.  The  coarser  phases  have  proved  of 
economic  importance  for  feldspar  at  Number  Four  Hill  in  the  western 
part  of  the  town  and  on  the  Hibbs  farm  north  of  Hebron  village,  and 
gem  tourmalines  and  various  mineral  specimens  have  been  obtained  at 
Mount  Rubellite,  about  2 miles  northeast  of  Hebron  village. 

Hibbs  feldspar  and  mica  mine. — A small  feldspar  and  mica  mine  was 
opened  in  1906,  about  1^  miles  north  of  Hebron  village  near  the 
Buckfield  road.  It  is  located  on  the  farm  of  Alton  Hibbs  and  was 
operated  during  1906  by  J.  A.  Gerry,  of  Mechanic  Falls,  and  W.  Scott 
Robinson.  It  was  abandoned  in  1907.  The  property  was  visited 
by  the  writer  in  August,  1906,  after  considerable  stripping  and  pros- 
pecting had  been  done.  The  ledge  was  exposed  for  a distance  of  300 
to  350  feet  along  the  southwest  side  of  a small  creek  valley,  the 


a Described  by  S.  L.  Penfield,  Am.  Jour.  Sci.,  3d  ser.,  vol.  47, 1894,  p.  337. 


OXFORD  COUNTY. 


73 


average  width  of  outcrop  being  about  30  feet,  though  increasing  to 
50  feet  at  at  least  one  point;  only  shallow  excavations  had  been 
made.  The  exposures  show  numerous  masses  of  pure  orthoclase- 
microcline  feldspar  2 to  3 feet  across,  associated  with  much  graphic 
granite.  The  spar  is  mottled  buff  to  blue-gray.  Small  amounts 
of  the  soda  feldspar,  albite,  are  found.  The  principal  iron-bearing 
impurity  is  black  tourmaline,  so  aggregated  that  it  can  be  readily 
separated  in  the  mining.  It  was  estimated  that  feldspar  of  commer- 
cial grade  for  pottery  purposes  formed  about  60  per  cent  of  the  rock 
mined.  Biotite  is  present  in  the  usual  lath-shaped  crystals  up  to 
1 foot  wide  and  3 feet  long  but  is  not  at  all  abundant. 

Muscovite  is  found  in  most  parts  of  the  pegmatite  in  small  books 
up  to  2 to  3 inches  across;  but  it  occurs  in  abundance  and  in  larger 
plates  only  at  the  southwestern  border  of  the  mass,  where  in  a zone 
averaging  3 to  4 feet  in  width  the  mica  books  average  5 inches  in 
diameter  and  one  reaches  30  inches;  this  specimen,  however,  was 
imperfect.  It  is  estimated  that  in  this  zone  muscovite  constitutes 
on  the  average  at  least  10  per  cent  and  sometimes  20  per  cent  of  the 
rock.  Ofthisitwas 
estimated  that  fully 
60  per  cent  could  be 
trimmed  into  plates, 
the  remainder  being 
usable  only  as  scrap 
mica.  Wedge struc- 


NE. 


-Micaceous  band 


ture  and  rulin°*  are  Figure  6.— Relations  of  pegmatite  and  wall  rock  at  Hibbs  feldspar  and 

mica  mine,  Hebron. 

the  common  de- 
fects. Plates  as  large  as  5 by  6 inches  could  be  trimmed  from  a few 
o'f  the  mica  books. 

Exposures  are  not  numerous  enough  to  reveal  the  full  form  or 
extent  of  the  pegmatite  mass.  On  its  southwest  side  it  is  bounded 
by  quartz-mica  schists,  which  trend  from  N.  30°  W.  to  N.  50°  W., 
averaging  about  N.  45°  W.,  and  apparently  dip  about  45°  NE.  The 
northeast  border  of  the  deposit  is  wholly  obscured  by  drift.  The 
mica-rich  band  which  follows  the  southwest  margin  of  the  pegmatite 
mass  can  be  traced  for  300  to  350  feet — nearly  the  whole  distance 
through  which  the  pegmatite  mass  itself  is  exposed.  The  apparent 
relations  of  the  pegmatite  and  schist  are  shown  in  figure  6. 

From  the  exposures  at  the  time  of  the  writer’s  visit  this  property 
was  regarded  as  a promising  one  for  both  feldspar  and  mica  mining. 
It  seems  probable  that  further  stripping  will  show  that  the  deposit 
extends  northwest  and  southeast  of  the  present  exposures,  and  since 
it  seems  to  be  steeply  inclined  there  is  no  reason  why  it  should  not 
persist  in  good  quality  to  considerable  depth.  The  development 
work  was  suspended  for  reasons  wholly  aside  from  the  quality  of  the 


*74  PEGMATITES  AND  ASSOCIATED  KOCKS  OF  MAINE. 

deposit.  All  output  must  be  hauled  by  teams  3 miles  to  Hebron 
station,  on  the  Rangeley  division  of  the  Maine  Central  Railroad. 

Mount  Rubellite. — A hill  known  as  Mount  Rubellite,  situated  about 
2 miles  northeast  of  Hebron  village,  was  formerly  worked  to  a slight 
extent  for  its  gems  and  rarer  minerals  by  Augustus  Hamlin,  of  Bangor, 
and  Loren  B.  Merrill,  of  Paris.  The  writer’s  visit  was  made  in 
August,  1906. 

The  small  opening  exposes  a face  of  rock  about  5 feet  high  and  35 
feet  long  on  a southwest  ward  sloping  hillside.  The  pegmatite  re- 
sembles in  a general  way  that  at  Mount  Mica  (p.  86),  but  has 
yielded  few  pockets,  Mr.  Merrill  reporting  the  occurrence  of  only 
three  or  four,  one  of  which  was  about  3 feet  wide,  6 feet  long,  and  18 
inches  deep.  Buff-colored  orthoclase-microcline  feldspar  is  in  many 
places  so  penetrated  by  black  tourmaline,  the  principal  iron-bearing 
impurity,  as  to  be  useless  for  pottery  purposes,  but  a few  pure  masses 
5 feet  across  indicate  that  the  locality  may  be  worth  working.  At 
one  place  books  of  mica,  some  of  them  5 to  6 inches  across,  but 
mostly  smaller,  show  on  the  surface  of  the  unopened  ledge  above  the 
pit,  but  they  do  not  seem  to  form  a definite  vein.  Probably  some  of 
this  mica  could  be  marketed  in  connection  with  the  feldspar,  but  the 
indications  do  not  warrant  development  for  the  mica  alone. 

Colored  tourmalines  have  been  found  at  this  locality,  but  for  the 
most  part  in  the  solid  pegmatite  rather  than  in  pockets,  so  that  their 
excavation  without  shattering  was  not  practicable.  As  may  be  in- 
ferred from  the  name  given  to  the  locality,  the  pink  or  rubellite 
variety  was  of  common  occurrence. 

Other  minerals  from  this  locality  are  ambylgonite,  apatite  in  small 
opaque  green  crystals,  arsenopyrite,  beryl,  cassiterite  inclosed  in 
clevelandite,  childrenite,  cookeite,  damourite  (an  alteration  product 
of  tourmaline),  halloysite,  herderite,®  lepidolite, 6 pollucite6  (embed- 
ded in  the  “sand”  at  the  bottom  of  two  pockets),  and  vesuvianite. 

The  trend  or  extent  of  the  coarse  pegmatite  could  not  be  de- 
termined. 

It  is  possible  that  it  would  pay  to  work  this  locality  for  its  feldspar, 
mica,  and  occasional  gems,  but  it  would  probably  be  unprofitable 
to  work  it  for  any  one  of  these  alone.  The  haul  to  Hebron  station, 
on  the  Rangeley  branch  of  the  Maine  Central  Railroad,  is  about  3 
miles. 

Streaked  Mountain. — Streaked  Mountain,  in  the  extreme  north- 
west corner  of  the  town  of  Hebron,  shows  in  a striking  way  the  large 
size  which  some  of  the  masses  of  coarse  pegmatite  may  assume.  The 

a Wells,  H.  L.,  and  Penfleld,  S.  L.,  Am.  Jour.  Sci.,  3d  ser.,  vol.  44,  pp.  114-116,  1892,  also  3d  ser.,vol.  47, 
p.  333,  1894. 

b Clarke,  F.  W.,  Bull.  U.  S.  Geol.  Survey  No.  42,  1887,  p.  14. 

c Wells,  H.  L.,  On  the  composition  of  pollucite  and  its  occurrence  at  Hebron,  Me.:  Am.  Jour.  Sci., 
3d  ser.,  vol.  41,  1891,  pp.  213-220. 


OXFORD  COUNTY. 


Y5 

crest  of  this  mountain  trends  in  a northwest-southeast  direction  and 
was  examined  for  over  half  a mile  of  its  length.  The  width  of  out- 
crop examined  from  southwest  to  northeast  across  the  trend  of  the 
ridge  was  also  about  half  a mile.  T}ie  whole  area  traversed  and  the 
remainder  of  the  mountain  &o  far  as  it  could  be  seen  was  underlain 
almost  exclusively  by  coarse  pegmatite,  the  mountain  being^ssentially 
a 11  boss”  of  this  material.  Near  the  highest  part  a few  patches  of 
schist  a few  square  yards  in  surface  are  entirely  surrounded  by 
pegmatite.  Another  schist  mass  was  40  to  50  feet  wide  and  100  feet 
long.  It  was  bordered  on  three  sides  by  pegmatite,  its  fourth  contact 
being  obscured  by  vegetation.  These  masses  appear  to  be  entirely 
unconnected  with  any  large  schist  areas. 

The  pegmatite  is  of  the  usual  type,  being  an  association,  often 
in  graphic  intergrowtli,  of  quartz,  orthoclase-microcline,  muscovite, 
black  tourmaline,  and  subordinate  amounts  of  biotite.  In  a few 
places, -as  on  the  highest  part  of  the  mountain,  it  is  coarse  enough  to 
yield  feldspar  of  suitable  quality  for  pottery  purposes,  some  masses 
of  pure  potash  feldspar  being  2 to  3 feet  across  and  rather  coarse 
graphic  granite  being  abundant.  Its  inaccessible  location  would, 
however,  render  its  working  impracticable  under  present  conditions. 
Certain  portions  of  this  pegmatite  consist  almost  wholly  of  graphic 
granite,  intersected  by  blades  of  muscovite,  but  these  areas  grade  into 
others  characterized  by  a granular-pegmatitic  texture  and  containing 
the  same  minerals,  but  also  much  black  tourmaline  and  some  garnet. 

It  is  difficult  to  conceive  of  a mass  of  this  size  and  general  uni- 
formity crystallizing  under  anything  like  vein  conditions.  With 
high  gaspous  content  and  hence  high  mobility  it  would  be  natural 
to  expect  more  differentiation  both  in  texture  and  composition. 
Although  the  composition  of  the  pegmatite  magma  was  probably 
slightly  different  from  the  normal  granite  magma,  it  seems  probable 
that  the  rigidity  of  the  mass  was  not  greatly  less  than  that  which 
would  characterize  a granite  boss  of  similar  dimensions. 

Mills  feldspar  quarry. — A small  abandoned  feldspar  quarry,  situ- 
ated on  Number  Four  Hill,  near  the  Paris-IIebron  line,  was  visited  by 
the  writer  in  August,  1906.  The  quarry  was  worked  by  the  Mount 
Marie  Mining  Company  in  1901  but  was  soon  abandoned. 

The  principal  pit  is  about  75  feet  long  by  30  feet  wide  and  10  feet 
in  maximum  depth.  A second  pit  close  by  is  about  30  by  30  feet  and 
10  feet  deep. 

The  bulk  of  the  feldspar  belongs  to  the  potash  varieties,  orthoclase, 
and  microcline,  though  some  albite  of  the  clevelandite  variety  occurs 
in  the  coarser-grained  portions.  In  the  northwestern  part  of  the 
larger  pit  some  masses  of  pure  spar  are  3 to  4 feet  across.  The  bare 
ledge  to  the  north  of  the  smaller  pit  for  a length  of  40  or  50  feet  and 
a width  of  about  30  feet  shows  feldspar  in  crystals  2 to  4 feet  across 


76  PEGMATITES  AND  ASSOCIATED  ROCKS  OF  MAINE. 

but  containing  numerous  small  crystals  of  black  tourmaline.  In  the 
larger  pit  there  is  a small  amount  of  feldspar  of  commercial  grade  at 
its  northwest  end,  but  in  the  smaller  pit  and  in  the  unopened  ledge 
near  the  pits  black  tourmaline  is  so  intimately  and  abundantly 
associated  with  the  feldspar  as  to  render  most  of  the  latter  valueless 
for  pottery  purposes  under  present  commercial  conditions.  The 
coarsest  and  most  highly  feldspathic  portion  of  the  deposit  as  exposed 
in  the  larger  pit  contains  some  clevelandite  and  granular  lepidolite 
and  a few  colored  tourmalines  of  pink  and  green  tints,  which  are 
translucent  to  opaque.  A few  small  pockets  occur  and  several  less 
than  a foot  in  diameter  were  exposed  at  the  time  of  the  writer’s  visit. 
In  some  of  the  pockets  a few  transparent  tourmalines  of  gem  quality 
were  found  during  the  mining  operations.  South  of  the  workings 
the  ledge  shows  very  little  feldspar  of  pottery  grade  and  within  200 
feet  there  begins  to  be  some  admixture  of  schist  with  the  pegmatite. 

Muscovite  has  been  saved  during  the  mining,  but  most  of  it  is  what 
is  known  as  wedge  mica  and  would  be  valueless  except  as  a source  of 
ground  mica.  Biotite  or  black  mica  is  very  rare,  black  tourmaline 
being  the  principal  iron-bearing  impurity. 

The  trend  and  exact  limits  of  this  deposit  could  not  be  determined, 
but  there  is  every  indication  that  the  supply  of  feldspar  suitable  for 
use  in  the  pottery  trade  is  very  small,  most  of  the  material  showing 
too  great  an  abundance  of  black  tourmaline.  An  examination  of  the 
whole  coast  of  the  hill  south  of  the  pits  showed  no  spar  or  other 
minerals  of  commercial  grade.  Even  if  the  mica  and  tourmalines 
were  marketed  as  accessories  it  is  probable  the  deposit  could  not  be 
made  to  pay. 

No  mining  machinery  was  installed  at  this  locality.  The  feldspar 
was  hauled  5 miles,  mostly  down  grade,  to  South  Paris,  on  the  Grand 
Trunk  Railway.  Only  a few  tons  of  it  was  shipped,  and  much  spar 
now  lies  in  stock  piles  at  the  quarry. 

NEWRY. 

The  rocks  of  Newry  were  studied  only  in  the  extreme  northeast 
corner  of  the  town  at  a quarry  formerly  operated  for  gem  tourmalines. 

The  Dunton  tourmaline  mine  is  situated  near  the  summit  of  a 
considerable  hill  that  rises  back  of  the  farm  of  Joshua  Abbott, 
about  1 to  1J  miles  west  of  the  wagon  road  between  North  Rumford 
and  South  Andover.  It  was  operated  in  the  summers  of  1903  and 
1904  by  H.  C.  Dunton,  of  Rumford  Falls. 

The  pegmatite  mass  appears  to  be  sill-like  in  form,  with  an  average 
thickness  of  about  20  feet  and  a dip  of  about  40°  SE.  The  wall  rock 
has  been  intensely  altered,  but  whether  this  is  largely  due  to  contact 
metamorphism  by  the  pegmatite  is  uncertain.  It  is  a light-green 
rock,  exceedingly  tough,  and  is  composed  largely  of  muscovite,  actin- 


OXFORD  COUNTY.  77 

olite,  and  quartz,  with  a little  acidic  plagioclase.  The  mineral  grains 
interlock  with  no  trace  of  schistose  structure. 

The  higher  slopes  of  the  mountain  between  the  mine  and  the  wagon 
road  show  much  pegmatite,  but  the  lower  slopes  near  the  road  are 
principally  a quartz-mica  schist,  which  is  shown  by  locally  recog- 
nizable bedding  planes  to  be  of  sedimentary  origin.  ^ 

The  pegmatite  mass  is  of  exceedingly  coarse  texture,  and  the 
principal  minerals  are  quartz,  orthoclase-microcline,  muscovite, 
bladed  albite  (clevelandite),  spodumene,  lepidolite,  and  tourmaline, 
with  beryl,  columbite,  and  autunite  as  minor  constituents. 

The  quartz  and  orthoclase-microcline  are  commonly  in  graphic 
intergrowth,  as  are  also  quartz  and  muscovite.  Orthoclase  is  the 
dominant  feldspar  in  most  parts  of  the  pegmatite  mass.  The  musco- 
vite is  not  of  com- 
mercial quality,  de- 
fects of  twinning, 
wedge  structure,  and 
A structure  being 
common.  Many 
muscovite  plates 
inclose  crystals  of 
transparent  green 
tourmaline,  some  of 
those  observed  be- 
ing one-fourth  inch 
wide  and  2 to  3 inches 
long.  None  are  large 
enough  or  perfect 
enough  to  yield 
gems. 

The  central  5 or  6 
feet  of  the  sill-like 
mass  of  pegmatite  constitutes  the  gem-bearing  zone  and  is  character- 
ized by  a different  mineral  association.  Quartz,  orthoclase-micro- 
cline, and  muscovite  occur,  but  clevelandite  is  locally  more  abundant 
than  potash  feldspar;  some  of  its  bladelike  crystals  are  10  to  12 
inches  in  length.  With  it  is  closely  associated  lepidolite,  usually  in 
small  aggregates,  but  occasionally  in  large  masses ; one  mass  measured 
6 by  2 by  3 feet  but  inclosed  some  clevelandite  and  pink  tourmaline. 
The  lepidolite,  as  at  most  of  the  gem  localities,  forms  granular  aggre- 
gates of  minute  plates  and  prisms.  Spodumene  occurs  in  flat  crystals, 
some  of  which  are  feet  in  length;  it  is  opaque  and  mostly  white, 
though  pale  pink  tints  are  sometimes  found.  Elongate  fluid  inclu- 
sions, nearly  all  of  which  are  elongate  parallel  to  the  principal  cleav- 
age and  contain  vacuoles,  are  abundant  in  this  spodumene;  their 
size  and  shape  are  shown  in  figure  7. 


ClPT 

\ 

^31 


33: 


Cleavage  direction  ^ 

cms  Qa: 


c 'Ey 


mz? 


Figure  7.— Fluidal  cavities  in  spodumene  from  Newry. 


78  PEGMATITES  AND  ASSOCIATED  ROCKS  OF  MAINE. 

Most  of  the  tourmaline  is  an  opaque  dark  blue-green,  though  some 
is  nearly  black.  Association  of  this  variety  with  the  clevelandite 
is  particularly  common.  Other  tourmalines  of  lighter  color  are  also 
abundant,  particularly  varieties  characterized  by  pink  centers  sur- 
rounded by  borders  of  light  grass  green.  Some  of  these  crystals  are 
transparent  in  part  and  have  yielded  gem  material,  but  they  are 
inclosed  in  the  solid  pegmatite  and  are  difficult  to  remove  without 
shattering.  Some  of  the  pink  and  green  tourmalines  are  of  large 
size,  one  being  reported  as  4 to  5 inches  across  and  about  2 feet  long; 
the  larger  ones,  however,  are  not  of  gem  transparency.  So  far  as 
known  no  pockets  have  been  encountered. 

Beryl  was  not  seen  in  place,  but  a small  loose  crystal,  though 
flawed,  was  perfectly  transparent  and  almost  deep  enough  in  color 
to  be  classed  as  emerald.  Autunite  occurs  in  crystals,  few  of  them 
over  one-sixteenth  of  an  inch  across,  embedded  in  or  lying  between 
plates  of  clevelandite.  Most  of  it  has  wholly  decomposed,  leaving  a 
small  cavity  and  a canary-yellow  stain  in  the  surrounding  feldspar. 

The  locality  was  abandoned  because  the  tourmalines  could  not  for 
the  most  part  be  removed  from  the  ledge  without  being  shattered  so 
much  as  to  destroy  their  gem  value.  If  further  excavation  should 
reveal  the  presence  of  pockets  in  this  pegmatite,  some  of  these  would 
almost  certainly  contain  gem  tourmalines  which  could  be  excavated 
by  careful  mining.  In  view  of  the  fact  that  no  pockets  have  yet  been 
found  it  seems  rather  doubtful  if  further  excavation  will  reveal  any. 

NORWAY. 

The  rocks  of  the  town  of  Norway  are  largely  quartz-mica  schists 
intimately  injected  by  pegmatite.  No  commercially  important  peg- 
matite deposits  are  known  to  occur,  but  some  localities  are  of  interest 
to  the  mineral  collector. 

At  Tubbs  Ledge,  2 miles  northwest  of  Norway  village,  a pegmatite 
mass  which  has  been  blasted  at  several  localities  in  a pasture  shows 
orthoclase,  white  quartz,  rose  quartz,  clevelandite,  black  and  green 
tourmalines,  and  lepidolite,  the  latter  a granular  aggregate  of  unusu- 
ally small  plates.  The  presence  of  lepidolite,  colored  tourmalines, 
and  clevelandite  shows  that  the  locality  is  a favorable  one  for  further 
prospecting  for  gem  tourmalines. 

In  the  northeast  corner  of  the  town  near  Cobble  Hill  and  near  the 
road  corners  due  southwest  of  West  Paris  a pegmatite  ledge  opened  by 
George  Howe,  of  Norway,  has  yielded  small  but  perfect  crystals  of 
chrysoberyl,  zinc  spinel,  and  zircon.  The  pegmatite  containing  these 
minerals  shows  distinct  evidence  in  a somewhat  schistose  structure 
and  slickensided  talcose  surfaces  of  some  movement  since  solidifica- 
tion. The  chrysoberyl  is  clearly  an  original  constituent,  but  the 
minute  zircons  one-sixteenth  to  one-eighth  inch  in  length  lie  upon 


OXFORD  COUNTY. 


79 


the  talcose  slickensided  surfaces  and  were  probably  formed  during 
the  shearing  process. 

Two  dikes,  cutting  pegmatite  of  moderate  coarseness  in  a roadside 
exposure  in  the  eastern  part  of  Norway,  are  instructive.  One  dike, 
ranging  from  G inches  to  3 feet  in  width,  is  a coarse  aggregate  of  quartz 
(some  rose  colored),  feldspar,  muscovite,  and  black  tourmaline;  it  is  not 
separated  from  the  wall  rock  by  sharp  boundaries.  The  other  dike 
is  similar  in  texture  and  mineral  composition,  but  has  quite  sharply 
defined  walls,  next  to  which  the  texture  is  less  coarse.  At  one  end, 
however,  this  dike  grades  imperceptibly  into  the  same  pegmatite  wall 
rock  which  it  elsewhere  intrudes  sharply.  These  are  plainly  examples 
of  contemporaneous  pegmatite  dikes. 

PARIS. 

The  writer’s  observations  extend  over  only  those  portions  of  the 
town  of  Paris  lying  between  South  Paris  and  Paris  and  from  there 
northeastward  to  the  Buckfield  line.  The  rocks  are  quartz-mica 
schists  intruded  by  pegmatite,  quartz  veins,  and  occasional  small 
trap  dikes.  The  schists  reveal  their  original  sedimentary  character 
in  the  preservation  here  and  there,  as  at  the  Crocker  Hill  mine  near 
Paris  Hill,  of  distinct  bedding  planes  due  to  an  alternation  of  highly 
quart zose  layers  with  others  that  are  more  argillaceous.  In  a few 
localities  small  beds  of  crystalline  limestone  occur  in  the  schists. 

The  collection  of  the  Sheffield  Scientific  School  of  Yale  University 
contains  some  fine  diamond-shaped  crystals  of  muscovite  from  the 
northern  part  of  the  town  of  Paris. 

The  only  locality  in  the  town  where  the  pegmatites  have  proved  of 
economic  importance  is  Mount  Mica,  near  Paris  Hill. 

HILL  NORTH  OF  CROCKER  HILL. 

Certain  relations  observed  on  the  next  large  hill  north  of  Crocker 
Hill,  about  2\  miles  from  Paris  village,  bear  on  the  origin  of  the  peg- 
matite and  their  physical  characters  at  the  time  they  were  intruded. 

Nearly  the  whole  hilltop  is  bare,  and  fully  three-quarters  of  the 
rock  is  a quartz-orthoclase-muscovite-black  tourmaline  pegmatite, 
which  has  been  broken  into  at  one  place  in  a search  for  beryl  of  gem 
quality.  At  this  opening  the  feldspar  is  sufficiently  free  from  black 
tourmaline  and  occurs  in  large  enough  crystals  to  be  of  commercial 
grade  for  pottery  purposes,  but  its  total  quantity  is  very  small,  most 
of  the  pegmatite  of  the  hill  being  too  quartzose  and  too  intimately 
shot  through  with  black  tourmaline  to  be  of  commercial  value  under 
present  conditions.  The  rock  associated  with  the  pegmatite  is  a 
schist  or  gneiss  similar  to  that  at  Mount  Mica,  but  more  intensely 
injected  by  quartz  and  feldspar  and  more  highly  garnetiferous.  It 
almost  certainly  represents  a schist  of  sedimentary  origin  subsequently 


80 


PEGMATITES  AND  ASSOCIATED  KOCKS  OF  MAINE. 


injected  by  pegmatitic  material.  Garnets  are  very  abundant  in  this 
gneiss  and  some  are  1J  inches  in  diameter.  There  are  also  some 
knots  or  lenticles  made  up  entirely  of  quartz  and  garnet  in  irregular 
association.  Most  of  these  are  under  1 foot  in  greatest  dimension, 
but  one  observed  was  8 feet  long  and  1J  feet  in  greatest  width. 
A band  2 to  3 feet  in  width  in  the  gneiss  and  traceable  for  about  25 
feet  is  fully  three-quarters  garnets  up  to  1J  inches  in  diameter,  the 
interspaces  being  occupied  by  quartz  and  some  feldspar.  In  all 
probability  this  profusion  of  garnets  is  a contact-met  amorphic  effect 
of  the  pegmatite  intrusion.  The  prevailing  strike  of  the  gneiss  is 
about  N.  45°  W. 

The  boundaries  of  the  larger  masses  of  pegmatite  may  parallel  the 
banding  of  the  gneiss  or  break  directly  across  it.  Considerable  dif- 
ferences exist  in  the  trend  of  the  gneiss,  even  in  outcrops  only  20  feet 
apart;  this  is  not  due  to  gradual  curving  of  the  folia,  the  changes 
being  abrupt  and  due  to  bodily  displacements  of  blocks  of  the  schist 
during  the  intrusion  of  the  pegmatite.  The  absence  of  any  great 
amount  of  softening  of  the  schist  consequent  on  the  intrusion  of  the 
pegmatite  is  also  well  illustrated  by  Plate  X,  A,  in  which  is  shown 
a pegmatite  mass  2 to  3 feet  across  and  a number  of  smaller  masses, 
all  intrusive  in  the  gneiss.  The  gneiss  folia  do  not  in  general  con- 
form to  the  outline  of  the  pegmatite  mass,  as  they  would  if  any  con- 
siderable amount  of  softening  of  the  schist  had  occurred,  and  only  in 
a zone  an  inch  or  two  wide  along  the  contact  of  the  gneiss  and  pegma- 
tite do  they  show  distortion.  Any  considerable  softening,  therefore, 
seems  to  have  been  confined  to  a zone  1 to  2 inches  wide.  The  bend- 
ing of  the  gneiss  folia  in  a manner  such  as  is  shown  in  the  figure  also 
indicates  that  the  pegmatite  when  intruded  behaved  to  a certain 
extent  like  a solid  body,  and  was  capable  of  exerting  differential 
thrust  on  its  inclosing  walls  of  gneiss.  In  a body  behaving  essen- 
tially like  a liquid,  pressure  would  become  equalized  in  all  directions, 
and  it  is  difficult  to  see  how  such  bending  could  have  been  produced. 

The  pegmatite  of  the  hill  is  cut  by  a number  of  quartz  veins  or 
dikes  mostly  under  6 inches  wide  and  mostly  subparallel  in  trend. 
Most  of  them  parallel  the  rather  poorly  defined  system  of  joints  in 
the  pegmatite.  Some  of  the  quartz  veins  possess  sharp  boundaries; 
others  are  rather  vaguely  delimited  from  the  bordering  pegmatite. 
Quartz  veins  of  the  latter  type  are  particularly  likely  to  contain 
some  feldspar  (orthoclase-microcline,  some  of  the  crystals  3 inches 
across)  and  some  muscovite  and  black  tourmaline.  Black  tourma- 
line is  also  found  frequently  in  veins  which  otherwise  are  composed 
wholly  of  quartz;  in  some  of  the  narrower  veins  it  may  be  even  more 
abundant  than  the  quartz.  The  two  often  show  interpenetration. 
At  one  place  the  relations  shown  in  figure  3 (p.  19)  were  observed 


OXFORD  COUNTY. 


81 


within  a space  3 or  4 feet  square.  The  pegmatite  is  in  sharp  contact 
with  the  gneiss,  into  which  it  sends  off  a tapering  apophysis.  The 
latter  for  a short  distance  from  the  main  pegmatite  mass  is  true 
pegmatite,  but  beyond  this  becomes  rapidly  more  quartzose.  Most 
of  this  branch  vein  consists  wholly  of  quartz. 

The  inferences  to  be  drawn  from  the  relations  described  may  be 
summarized  as  follows: 

(1)  The  relations  shown  in  Plate  X,  A,  and  the  fact  that  the 
changes  in  trend  of  the  schists  are  abrupt  and  due  to  displacement 
of  schist  blocks  en  masse  indicate  that  the  pegmatite  intrusions  pro- 
duced no  extensive  softening  of  the  schists.  Such  softening,  when 
present  at  all,  was  confined  to  a zone  an  inch  or  two  wide  immedi- 
ately adjacent  to  the  pegmatite.  (2)  The  bending  of  gneiss  folia 
next  the  pegmatite  (see  PL  X,  A)  suggests  that  the  dike,  even  before 
its  border  portions  had  entirely  solidified,  behaved  essentially  as  a 
rigid  body  capable  of  transmitting  differential  thrust  and  not  as  a 
liquid. 

The  relations  shown  in  figure  3,  the  fact  that  feldspar,  muscovite, 
and  black  tourmaline  occur  in  many  of  the  quartz  veins,  and  the 
fact  that  these  veins  are  in  some  places  not  sharply  differentiated 
from  the  inclosing  pegmatite,  indicate  that  at  least  many  of  the 
quartz  veins  are  to  be  regarded  as  end  crystallizations  from  the 
pegmatite  magma. 

MOUNT  MICA. 

History. — Mount  Mica,  a small  hill  situated  about  1^  miles  east 
of  the  village  of  Paris  at  an  elevation  of  approximately  900  feet,  is 
one  of  the  most  famous  mineral  localities  in  the  United  States,  and 
is  known  to  mineralogists  all  over  the  world  because  of  the  size  and 
beauty  of  its  tourmaline  crystals. 

The  discovery  of  its  mineral  wealth  dates  back  to  the  year  1820,® 
when  two  students,  Elijah  S.  Plamlin  and  Ezekiel  Holmes,  the  former 
a resident  of  the  town  of  Paris,  becoming  interested  in  the  study  of 
mineralogy,  spent  much  time  in  searching  for  minerals  in  the  exposed 
ledges  and  the  mountains  around  the  village.  In  returning  from 
one  of  their  expeditions  in  the  autumn  of  1820,  Hamlin’s  eye  was 
caught  by  a gleam  of  green  from  an  object  caught  in  the  roots  of  a 
tree  upturned  by  the  wind.  The  object  proved  to  be  a fragment  of 
a transparent  green  crystal  lying  loose  upon  the  earth  which  was 
still  attached  to  the  roots  of  the  tree.  This  was  the  first  colored 
tourmaline  taken  from  the  locality  which  afterwards  yielded  them 
so  prolifically,  but  its  character  was  not  recognized  until  somewhat 

a Hamlin,  A.  C.,  The  history  of  Mount  Mica,  Bangor,  Me.,  1895. 

63096°— Bull.  445—11 6 


82 


PEGMATITES  AND  ASSOCIATED  ROCKS  OF  MAINE. 


later,  when  the  same  students  sent  similar  crystals  for  identification 
to  Professor  Silliman,  of  Yale. 

The  winter’s  snows  setting  in  the  night  after  the  discovery  pre- 
vented further  exploration  until  the  following  spring,  when  the  two 
students  searched  the  bare  ledge  and  the  overlying  soil  and  were 
rewarded  with  thirty  or  more  crystals  of  tourmaline  of  remarkable 
beauty  and  transparency,  with  which  were  associated  masses  of  pur- 
plish red  to  pink  lepidolite  and  splendid  crystal  groups  of  white  and 
of  smoky  quartz. 

Subsequent  examination  indicated  that  the  ledge  was  perforated  with  cavities  in 
which  the  tourmalines  and  other  minerals  had  been  deposited  and  that  the  crystals 
that  had  been  gathered  by  the  students  had  been  set  free  from  their  cavities  by  the 
disintegration  of  the  surface  of  the  ledge.  Parts  of  the  ledge  were  fairly  honeycombed 
with  small  cavities  and  soft  spots  where  the  decomposing  feldspar  was  crumbling 
away.  In  these  cavities  and  decayed  places  other  tourmalines  were  obtained  by 
breaking  away  the  edges  of  the  cavities  or  removing  the  decomposed  material. a 

The  finding  of  the  first  of  the  large  pockets  is  described  by  Mr. 
Hamlin6  as  follows: 

Two  years  after  the  discovery  (1822),  the  two  younger  brothers  of  the  discoverer, 
Cyrus  and  Hannibal  Hamlin,  although  scarcely  in  tk»ir  teens,  resolved  to  make  a 
more  complete  exploration  of  the  ledge.  Having  borrowed  some  blasting  tools  in 
the  village,  they  proceeded  to  the  hill  and  managed  in  a rough  way  to  drill  several 
holes  in  the  ledge  and  blast  them  out.  These  operations,  though  of  trivial  magni- 
tude, were  attended  with  unlooked-for  results,  for  the  explosions  threw  out,  to  the 
astonishment  of  thu  boys,  large  quantities  of  bright-colored  lepidolite,  broad  sheets 
of  mica,  and  masses  of  quartz  crystals  of  a variety  of  hues.  The  last  blast  exposed  a 
decayed  place  in  the  ledge,  which  yielded  readily  to  the  thrusts  of  a sharpened  stick 
or  the  point  of  the  iron  drills.  As  the  surface  was  removed,  great  numbers  of  minute 
tourmalines  were  discovered  in  the  decomposed  feldspar  and  lepidolite.  The  rock 
became  softer  and  softer  as  the  boys  proceeded  in  their  work  of  excavation,  and  soon 
they  reached  a large  cavity  of  two  or  more  bushels  capacity.  This  hollow  place,  or 
rotten  place,  appeared  to  be  filled  with  a substance  resembling  sand,  loosely  packed. 
Amongst  this  sand  or  disintegrated  rock,  crystals  of  tourmaline  of  extraordinary  size 
and  beauty  were  found  scattered  here  and  there  in  the  soft  matrix.  Scratching  away 
with  renewed  energy,  the  boys  soon  emptied  the  pocket  of  its  contents,  and  found 
that  they  had  obtained  more  than  twenty  crystals  of  various  forms  and  hues.  One  of 
these  was  a magnificent  tourmaline  of  a rich  green  color  and  a remarkable  transpar- 
ency. It  was  more  than  2|  inches  in  length  by  nearly  2 inches  in  diameter,  and  both 
of  its  terminations  were  finely  formed  and  perfect. 

Several  others  possessed  extraordinary  beauty,  and  some  of  them  were  quite  3 
inches  in  length  and  an  inch  in  diameter.  The  colors  of  these  tourmalines  were  quite 
varied,  but  were  chiefly  red  and  green.  * * * The  exact  number  of  the  crystals 
obtained  by  the  boys  is  not  known,  but  when  collected  together  with  the  fragments 
of  others  they  filled  a basket  of  nearly  two  quarts  capacity.  Besides  the  tourmalines, 
the  quantity  of  lepidolite,  mica,  and  other  choice  minerals  thrown  out  by  the  blasts 
or  found  in  the  sides  of  the  cavity  was  so  great  that  the  boys  were  obliged  to  seek  for 
an  ox  team  to  transport  them  home. 

From  1822  until  1864  the  locality  was  visited  by  many  mineralo- 
gists, geologists,  and  mineral  collectors,  who  excavated  to  some  extent 


a Op.  cit.,  p.  10. 


b Op.  cit.,  pp.  11-12. 


GENERAL  VIEW  OF  THE  TOURMALINE  QUARRY  AT  MOUNT  MICA  IN  NOVEMBER,  1908.  LOOKING  WEST. 

The  upper  layers  of  rock  in  the  middle  ground  are  the  schist  capping.  In  the  foreground  is  the  gigantic  pocket  shown  in  Plate  XIII.  The  rock  at  the  right  is  waste,  piled  in  th< 

worked-out  portions  of  the  pit. 


OXFORD  COUNTY. 


83 


and  secured  a number  of  valuable  and  beautiful  tourmalines,  though 
no  systematic  working  was  attempted.  Observations  were  made 
by  Professor  Shepard,  of  Amherst  College,  between  1825  and  1830.a 

In  1864  Samuel  R.  Carter,  of  Paris,  commenced  work  in  front  of 
the  pit  made  by  former  explorers  and  started  a cut  in  the  ledge  40 
or  50  feet  to  the  west,  intending  to  strike  the  mineral  belt  at  a depth 
greater  than  had  before  been  reached,  but  after  removing  many  tons 
of  rock  and  finding  no  sign  of  the  deposit  he  stopped  work.  Shortly 
after  the  close  of  the  civil  war  A.  C.  Hamlin,  the  discoverer  of  the 
deposit,  made  a few  test  blasts  and  discovered  a small  pocket  showing 
green  tourmalines  touched  at  the  base  with  pink.  In  1871  he  renewed 
his  work  and  after  some  excavation  disclosed  a pocket  containing 
one  of  the  finest  crystals  of  white  tourmaline  (achroite)  that  has 
ever  been  found.  This  was  4J  inches  in  length  and  1J  inches  in 
diameter,  white  at  the  top,  but  changing  to  a smoky  hue  toward  the 
base,  and  tipped  at  both  ends  with  green.  It  is  now  in  the  miner- 
alogical  museum  of  Harvard  College.  About  1873  Mount  Mica  was 
worked  for  muscovite  by  a party  of  explorers  and  the  contents  of 
several  fine  pockets  which  they  opened  were  scattered  or  destroyed. 
About  1880,  in  order  to  continue  the  work  for  gem  minerals, 
Dr.  Hamlin  formed  the  Mount  Mica  Company  and  continued  to 
operate  intermittently  and  with  varying  degrees  of  success  until 
about  1886,  when  work  was  suspended  owing  to  the  belief  that  the 
deposit  did  not  extend  farther'  to  the  east.  In  1890  Loren  B. 
Merrill,  who  had  been  engaged  to  some  extent  in  gem  mining  at 
Mount  Apatite,  and  L.  Kimball  Stone,  both  of  Paris,  purchased  the 
rights  to  operate  the  property  and  have  worked  it  successfully  to 
the  present  time. 

Mount  Mica  was  visited  by  the  writer  in  August,  1906,  and  again 
in  October,  1907,  and  November,  1908.  In  1908  the  pit  was  about 
150  feet  long  from  northeast  to  southwest  and  from  50  to  100  feet 
wide.  The  maximum  depth  was  about  20  fedt.  W.  H.  Emmons, 
who  visited  the  mine  in  July,  1910,  reports  that  the  pit  was  then  300 
feet  long  and  35  feet  in  maximum  depth.  These  dimensions  do  not 
mark  the  total  area  which  has  been  worked  over,  for  most  of  the 
quarry  waste  has  been  piled  in  the  abandoned  workings.  Plate  XI 
gives  a general  view  of  the  quarry. 

Gem-bearing  zone. — As  at  most  of  the  Maine  quarries  where  peg- 
matite deposits  are  worked  the  relations  between  the  pegmatite  and 
the  wall  rock  and  between  pegmatite  of  various  degrees  of  coarseness 
are  very  irregular.  The  general  position  of  the  gem-bearing  zone  and 
its  relation  to  the  bordering  schists  is,  however,  rather  clear.  Figure 
8 represents  a section  through  the  mine  from  northwest  to  southeast, 


a Shepard,  C.  U.,  Mineralogical  journey  in  the  northern  parts  of  New  England:  Am.  Jour.  Sci.,  1st  ser., 
vol.  18,  1830,  pp.  293-303. 


84 


PEGMATITES  AND  ASSOCIATED  ROCKS  OE  MAINE. 


the  portions  excavated  previous  to  1908  being  inclosed  in  a dotted 
line.  As  shown  in  this  diagram,  the  Mount  Mica  pegmatite  mass  dips 
gently  20°  to  30°  SE.,  being  intruded  in  general  parallel  to  the  trend 
of  quartz-mica  schists,  which  at  the  quarry  strike  N.  50°  to  60°  E.  and 
dip  20°  to  30°  SE.  The  significance  of  certain  schist  fragments 
inclosed  in  the  pegmatite  is  discussed  on  page  135. 

The  schists  are  unquestionably  of  sedimentary  origin  but  are 
locally  so  much  injected  by  narrow  sheetlike  offshoots  from  the  larger 
pegmatite  masses  that  they  resemble  igneous  gneisses.  The  contact 
of  the  pegmatite  on  the  schist  is  generally  very  sharp  and  there  is  no 
indication  of  any  absorption  of  the  schist,  though  the  abundance  of 
garnets  near  the  contact  indicates  some  contact  metamorphism. 

The  whole  pegmatite  mass  is  not  productive  (see  fig.  8),  the  gem 
and  pocket  bearing  portion  constituting  a zone  ranging  from  a few 
inches  to  6 or  7 feet  in  thickness  lying  immediately  below  the  schist 
capping.  The  productive  layer  originally  outcropped  at  the  surface, 
a relation  to  which  was  due  its  discovery  and  the  ease  with  which  it 
was  worked  in  the  early  days.  At  present  the  southeastern  wall  of 

Portions  excavated 

N w previous  to  1908  S E. 


Schist  and  gneiss 
Pocket-bearing  zone 

Normal  unproductive 
pegmatite 

Figure  8. — Diagram  showing  geologic  structure  at  Mount  Mica  tourmaline  mine,  Paris. 

the  quarry  is  capped  by  about  10  to  15  feet  of  schist  which  must  be 
stripped  off  before  the  pocket-bearing  zone  is  reached.  According 
to  present  indications  increasingly  great  thicknesses  of  schist  must  be 
removed  as  the  workings  are  extended  to  the  southeast,  though  the 
pegmatite  may  show  irregularities  the  nature  of  which  can  not  be 
predicted.  If  the  work  is  extended  far  to  the  southeast  tunneling 
may  be  found  to  be  cheaper  than  stripping.  There  is  very  little 
question,  however,  that  further  lateral  excavation  to  the  southwest 
and  northeast  of  the  present  workings,  in  prolongation  of  the  original 
line  of  outcrop  of  the  pocket-bearing  zone,  would  disclose  a continua- 
tion of  the  productive  layer.  Prospecting  at  least  along  these  lines 
should  be  undertaken  before  the  excavations  are  carried  to  any  great 
depths  in  a southeast  direction  along  the  dip  of  the  deposit. 

The  gem-bearing  zone  is  not  very  sharply  differentiated  from  the 
pegmatite  below  it,  but  is  in  general  somewhat  coarser  and  is  sepa- 
rated from  the  underlying  unproductive  pegmatite  by  a narrow 
layer  very  rich  in  small  garnets.  This  layer  is  similar  to  the  garnet- 
iferous  bands  observed  at  the  Wade  and  Pulsifer  quarry  in  Auburn, 


geological  survey  bulletin  445  plate  xii 


The  position  of  each  pocket  is  marked  by  a stick  with  a white  card  attached.  (From  a negative  in  the  possession  of  Mr.  T.  F.  Lamp,  of  Portland.) 


OXFORD  COUNTY. 


85 


and  it  was  clearly  recognized  by  A.  C.  Hamlin  as  marking  the  line 
between  the  productive  and  unproductive  rock.  Out  of  the  80 
pockets  known  to  him  previous  to  1895,  not  one  was  found  below  this 
garnetiferous  layer,  nor  have  later  excavations  revealed  any.  The 
pocket-bearing  zone  is  further  differentiated  from  the  rest  of  the  peg- 
matite by  the  abundance  of  clevelandite,  lepidolite,  and  some  other 
minerals  not  found  elsewhere. 

Pockets. — An  idea  of  the  abundance  of  pockets  may  be  gained  from 
Plate  XII,  a reproduction  of  an  old  photograph  showing  the  workings 
at  a time  when  the  pocket-bearing  zone  could  be  reached  by  very 
shallow  excavation.  In  this  picture  the  position  of  each  pocket  is 
shown  by  a small  stick  with  a white  card  attached.  The  abundance 
of  pockets  differs  greatly  in  different  parts  of  the  mineral  zone,  as 
does  also  their  richness  in  tourmalines,  so  that  certain  portions  of  the 
productive  zone  have  proved  much  more  valuable  than  others.  Most 
of  the  pockets  are  more  or  less  spherical  in  outline,  but  some  are  very 
irregular,  many  consisting  of  several  connected  cavities.  Few  of 
them  are  angular  in  form.  One  that  may  be  regarded  as  of  average 
shape,  though  somewhat  above  the  average  in  size,  is  shown  in 
Plate  IX,  B,  and  is  3 feet  in  diameter.  In  size  they  vary  from  those 
having  a capacity  of  only  about  a pint  to  one  which  was  20  feet  long, 
12  feet  wide,  and  7 feet  high  and  contained  three  connecting  chambers. 
This  largest  known  pocket  is  shown  in  Plate  XIII.  One  pocket  6 feet 
below  the  surface  of  the  ledge,  found  in  1868,  was  scarcely  larger  than 
the  hand  and  contained  nothing  but  one  transparent  tourmaline 
crystal  3 inches  long  and  1 inch  in  diameter.®  The  total  number  of 
pockets  found  up  to  October,  1907,  was  estimated  at  430,  of  which  350 
have  been  found  by  Merrill  & Stone,  the  present  operators.  Only  a 
small  proportion,  however,  yielded  any  gem  material;  out  of  60 
opened  by  Merrill  & Stone  in  one  autumn,  only  five  or  six  yielded 
anything  of  value,  and  out  of  the  entire  350  opened  by  them  only 
about  50  were  worth  much. 

According  to  Dr.  Hamlin, 6 “The  cavities  generally  were  roofed 
with  albite,  whilst  the  sides  were  composed  of  limpid  or  smoky  quartz 
mixed  with  lepidolite,  crystals  of  tin  (cassiterite),  spodumene,  am- 
blygonite,  and  other  rare  minerals.” 

Few  pockets  were  observable  at  the  time  of  the  writer’s  visit,  but 
Hamlin’s  description  is  probably  essentially  correct,  although  albite 
was  not  observed  to  be  any  more  abundant  above  the  pockets  than 
below  them  or  at  their  sides. 

The  action  of  frost  and  percolating  water  has  in  most  places  pro- 
duced much  disintegration  in  the  walls  of  the  cavities,  and  their  floors 
are  generally  formed  of  a sandy  or  clayey  mass  consisting  of  partly 
decomposed  fragments  of  clevelandite  and  lepidolite  associated  in 


a Hamlin,  A.  C.,  The  history  of  Mount  Mica,  p.  63  and  PI.  XV 


b Idem,  p.  49. 


86 


PEGMATITES  AND  ASSOCIATED  ROCKS  OP  MAINE. 


greater  or  less  abundance  with  kaolin  and  the  hydromica  cookeite. 
In  this  mass  of  decomposed  material  the  tourmalines  are  embedded. 
There  can  be  no  doubt  that  they  were  once  attached  to  the  walls  of 
the  cavities,  but  they  have  been  loosened  from  their  original  position, 
many  being  fractured  in  the  process,  and  now  lie  in  every  conceivable 
position  in  the  material  forming  the  floor  of  the  cavity.  Many  of  the 
groups  of  quartz  crystals  which  adorned  the  walls  have  been  loosened 
in  a similar  way,  some  of  them  now  lying  embedded  in  the  materials 
of  the  floor  with  the  apices  of  the  crystals  downward  just  as  they  fell 
from  the  roof  of  the  cavity.  In  some  of  the  cavities  the  amount  of 
kaolinic  material  is  very  large,  about  a ton  of  the  pink  kaolin  mont- 
morillonite  having  been  taken  from  the  large  one  shown  in  Plate 
IX,  B . 

Minerals. — The  bulk  of  the  pegmatite  found  at  this  quarry  is  in 
general  similar  to  that  at  other  pegmatite  workings  in  Maine  but 
differs  from  these  in  the  relative  scarcity  of  graphic  intergrowths  of 
quartz  and  potash  feldspar.  The  principal  constituent  minerals  are 
quartz,  orthoclase  and  microcline,  muscovite,  biotite,  and  black  tour- 
maline, and  their  association  seems  to  be  wholly  irregular.  Even  in 
the  pocket-bearing  layer  these  are  the  principal  minerals,  though  here 
the  clevelandite  variety  of  albite,  lepidolite,  and  colored  tourmalines 
are  also  found. 

Quartz  is  present  in  the  solid  pegmatite,  principally  in  small  irreg- 
ular opaque  masses  which  are  white  to  slightly  smoky  in  color. 
Rarely  it  is  graphically  intergrown  with  feldspar.  In  the  pockets  it 
occurs  as  groups  of  very  perfectly  developed  transparent  colorless 
crystals.  Where  these  have  become  detached  from  the  walls  they 
may  lie  embedded  in  kaolin  and  cookeite  in  the  bottom  of  the 
pockets. 

The  principal  feldspar  is  buff-colored  orthoclase  and  microcline, 
occurring  mainly  in  small,  irregular  masses  intergrown  with  the  other 
common  pegmatite  minerals.  A very  few  masses  of  pure  feldspar  as 
much  as  2 J feet  across  were  observed.  The  dump  is  now  (1910)  being 
picked  over  by  the  Maine  Feldspar  Company,  of  Auburn,  to  obtain 
spar  for  pottery  purposes,  but  before  this  the  feldspar  was  not 
utihzed  in  any  way.  In  the  pocket-bearing  zone  pure  white  albite 
of  the  clevelandite  variety  is  abundant,  associated  particularly  with 
lepidolite,  muscovite,  and  quartz. 

Muscovite  occurs  in  graphic  intergrowth  with  quartz  and  also  in 
books,  many  of  which  are  5 to  6 inches  across.  One  seen  on  the 
waste  pile  was  12  by  14  inches  in  size,  and  another  was  1 foot  long 
and  7 to  8 inches  wide.  A few  of  the  books  inclose  long,  slender 
crystals  of  opaque  green  tourmaline,  the  largest  observed  being 
4 inches  long  and  one-fourth  inch  in  diameter.  The  finest  musco- 
vite crystal  from  this  locality  known  to  the  writer  is  in  the  public 


BULLETIN  445  PLATE  XIII 


LARGEST  POCKET  EVER  FOUND  AT  MOUNT  MICA. 


OXFORD  COUNTY. 


87 


library  at  Paris  and  is  a clear,  perfect  piece  of  roughly  hexagonal 
outline,  measuring  about  8 by  2J  inches.  Good  specimens  of  plumose 
mica,  produced  by  close-spaced  ruling,  are  also  to  be  found  in  the 
collections  at  Paris.  Where  not  too  intimately  mixed  with  other 
minerals,  the  mica  is  saved  in  the  quarrying  process  and  has  brought 
$25  per  ton  as  taken  from  the  quarry.  At  another  time  12J  cents  per 
pound  was  offered  for  the  thumb-trimmed  product.  The  largest 
perfect  plates  of  cut  mica  obtained  from  this  material  would  prob- 
ably not  exceed  3 by  4 inches  in  size.  Much  is  defective  owing  to 
wedge  structure  and  ruling  and  is  valuable  only  as  scrap  mica. 

Biotite  is  not  abundant,  but  it  occurs  in  a few  places  in  its  usual 
form  of  long,  narrow,  and  very  thin  crystals,  the  largest  seen  being  10 
inches  long  and  one-half  inch  wide. 

Lepidolite  or  lithium  mica  is  of  common  occurrence  in  the  pocket- 
bearing portions  of  the  pegmatite.  The  largest  mass  found,  though 
impure,  is  reported  as  weighing  10  tons,  and  it  is  not  difficult  to  obtain 
fairly  pure  masses  8 or  10  inches  across.  The  mineral  occurs  mostly 
in  the  granular  forms,  though  some  curved  and  globular  crys- 
tals have  been  found.  The  color  varies  from  lavender  to  peach- 
blossom  pink.  The  granular  varieties  commonly  show  some  admix- 
ture of  quartz,  muscovite,  and  clevelandite  and  not  uncommonly 
contain  interbedded  crystals  of  opaque  pink  and  more  rarely  green 
tourmaline;  some  specimens  which  have  been  sawed  into  small  blocks 
and  polished  make  handsome  paperweights.  Lepidolite  from  this 
locality  has  been  described  by  Clarke,  who  also  gives  analyses. a 

Black  tourmaline  or  schorl,  which  is  the  most  abundant  iron- 
bearing mineral  present  at  the  quarry,  occurs^in  prismatic  crystals, 
mostly  compound,  many  of  which  are  a foot  in  length  and  4 to  5 
inches  in  diameter.  A few  having  a length  of  2\  feet  were  seen  by 
the  writer,  and  one  4 feet  in  length  is  described  by  Hamlin.  A few 
large  compound  prisms  of  black  tourmaline  separate  at  their  ends 
into  a brushlike  aggregate  of  small  prisms,  the  interspaces  being  filled 
with  quartz  and  an  aggregate  of  minute  muscovite  scales.  The  black 
tourmalines  occur  in  the  solid  pegmatite,  penetrating  it  in  all  direc- 
tions; except  for  a few  small  crystals,  they  have  never  been  found  in 
pockets.  Some  colored  tourmalines  occur  in  the  solid  pegmatite  near 
the  pockets,  associated  usually  with  clevelandite,  muscovite,  lepido- 
lite, and  quartz;  a few  of  these  are  curved  through  considerable 
angles.  Most  of  these  colored  crystals  are  opaque,  though  a few 
small,  delicate,  transparent  ones  are  interleaved  with  muscovite. 
Fine  specimens  of  these  latter  are  found  in  the  Carter  collection  in 
the  public  library  at  Paris;  other  specimens  are  much  larger,  some 
containing  interleaved  tourmalines  3 or  4 inches  in  length  and 
one-fourth  inch  or  so  in  thickness.  In  a few  instances  tourmalines 


a Clarke,  F.  W .,  Lepidolite  of  Maine:  Bull.  U.  S.  Geol.  Survey  No.  42,  1887,  p.  13. 


88  PEGMATITES  AND  ASSOCIATED  ROCKS  OF  MAINE. 

cross  each  other  with  mutual  penetration  about  at  right  angles,  but 
most  commonly  several  crystals  diverge  from  single  points,  forming 
fan-shaped  aggregates  extending  through  60°,  90°,  or  even  100°. 

None  of  the  above-described  tourmalines  are  of  gem  value. 

Amblygonite  is  the  only  other  mineral  occurring  at  all  abundantly 
in  the  pegmatite.  It  is  found  only  as  a constituent  of  the  solid 
pegmatite  in  irregular  masses  often  4 to  8 inches  across.  One  mass 
is  estimated  to  have  weighed  nearly  800  pounds.  The  mineral  usually 
occurs  near  the  pockets  and  is  regarded  as  an  indicator  of  their 
proximity. 

Spodumene  occurs  in  opaque  gray  flat  crystals,  usually  associated 
with  lepidolite.  One  crystal  measured  2 feet  long,  7 inches  wide, 
and  2 inches  thick.  Portions  of  a few  of  the  crystals  are  a trans- 
parent pale  blue  or  pink.  According  to  Mr.  Merrill,  an  abundance 
of  beryl  or  spodumene  about  a pocket  generally  signifies  that  the 
latter  contains  few  if  any  tourmalines.  A white  spodumene  crystal 
in  the  Hamlin  collection  at  Paris  is  7 inches  long  and  4 inches  thick 
and  is  split  by  a wedge-shaped  mass  of  granular  lepidolite  tapering 
from  1 inch  to  one-lialf  inch  in  thickness. 

Apatite  occurs  in  the  solid  pegmatite  in  irregular  opaque  green 
masses,  some  few  of  which  weigh  a couple  of  pounds.  A small 
deep-blue  bipyramidal  crystal  one-fourth  inch  in  length  with  crystal 
faces  developed  in  remarkable  perfection  has  been  described  and 
figured  by  Prof.  E.  S.  Dana.a 

Cassiterite  occurs  rarely,  usually  associated  with  clevelandite  near 
the  pockets.  Some  crystals  are  found  embedded  in  the  sandlike 
materials  at  the  bottom  of  the  pockets. 

Columbite  is  rare  and  usually  occurs  in  irregular  bladelike  crystals. 

Arsenopyrite  was  observed  in  veinlike  masses,  mostly  one-eighth  to 
one-fourtli  inch  in  width  and  2 or  3 inches  in  length,  flanked  by 
irregular  borders  of  quartz,  which  in  turn  are  irregularly  bordered 
by  orthoclase  and  microcline.  The  arsenopyrite  therefore  virtually 
forms  the  central  portion  of  small  contemporaneous  quartz  veins  or 
lenses  in  the  pegmatite. 

Triphyllite  occurs  mostly  in  aggregates,  many  of  which  weigh 
from  10  to  20  pounds  and  a few  as  much  as  50  pounds. 

Zircons  occur  mostly  associated  with  triphyllite,  few  crystals  being 
over  one-eighth  inch  in  diameter. 

Kaolin  occurs  in  considerable  amounts  in  the  bottoms  of  some  of 
the  pockets  as  a decomposition  product  of  feldspar.  In  the  giant 
pocket  shown  in  Plate  XIV  over  a ton  of  the  pink  kaolin  montmoril- 
lonite  was  aggregated  at  one  end  of  the  pocket. 

Other  minerals  found  at  Mount  Mica  are  autunite,  brookite,  chil- 
drenite,  damourite,  halloysite,  lollingite,  petalite,  pyrite,  sphalerite, 


a Am.  Jour.  Sci.,  3d  ser.,  vol.  27,  1884,  p.  480. 


U.  S.  GEOLOGICAL  SURVEY 


BULLETIN  445  PLATE  XIV 


LARGEST  CRYSTAL  OF  TOURMALINE  EVER  FOUND  AT  MOUNT  MICA. 


Length,  1 5£  inches;  maximum  width,  7 inches;  weight,  31-^  pounds, 


OXFORD  COUNTY. 


89 


yttrocerite,  and  zircon.  Cookeite  from  Mount  Mica  has  been 
described  in  detail  by  Penfield.® 

Gems. — The  gem  tourmalines  of  this  locality  show  remarkable 
variety  in  form,  size,  and  color.  Those  of  value  occur  without 
exception  in  the  pockets,  usually  but  not  invariably  detached  from 
their  original  position  on  the  walls  and  lying  at  the  bottom  in  a 
sandlike  matrix  of  kaolin  and  cookeite.  Most  of  them  range  in  color 
from  olive  green  through  emerald  green  to  blue  green;  some  are  nearly 
colorless,  some  show  beautiful  pink  tints,  and  the  central  portions 
of  some  are  a deep  ruby  red  when  viewed  along  the  main  crystal 
axis;  a few  are  the  color  of  amber  and  of  port  wine;  and  some  are  a 
purplish  red.  Many  show  a zonal  distribution  of  colors.  A polished 
cross  section  of  a crystal  about  three-fourths  of  an  inch  in  diame- 
ter, preserved  in  the  Cambridge  Museum  of  Natural  History,  shows 
a blue-green  center  about  one-half  inch  across,  surrounded  by  a 
transparent  pink  border  one-eighth  inch  wide,  outside  of  which  is  a 
pale  transparent  olive-green  border  about  one-sixteenth  inch  wide. 
Crystals  with  pink  centers  and  olive-green  borders  are  not  uncommon. 
One  shade  commonly  predominates  in  a pocket,  but  some  pockets 
contain  gems  of  different  colors.  Some  single  crystals  shade  from 
white  at  one  termination  to  emerald  green,  then  to  light  green  and 
pink,  and  finally  to  colorless  at  the  other  termination.  Green  crystals 
tipped  with  pink  are  especially  common.  Generally  these  transitions 
of  color  are  very  gradual,  but  in  some  specimens  the  colors  are  not 
mingled  in  the  least,  and  the  crystals,  though  crystallographically  con- 
tinuous throughout,  seem  to  be  composed  of  several  distinct  sections. 

In  some  pockets  the  tourmalines  when  first  disclosed  lie  in  apparent 
perfection  of  form  and  color  in  their  clayey  matrix,  but  crumble 
away  as  soon  as  touched.  In  others  certain  portions  only  of  the 
crystals  crumble  away,  leaving  a smooth  nodule  of  perfectly  fresh 
tourmaline,  usually  beautifully  transparent  and  in  form  resembling 
somewhat  the  nodules  produced  by  the  etching  of  quartz  crystals 
with  hydrofluoric  acid.  Some  of  the  finest  gems  have  been  cut  from 
such  nodules.  Some  hollow  crystals  of  tourmaline  are  found,  com- 
monly of  small  diameter,  but  including  some  as  much  as  an  inch  in 
length;  they  were  probably  produced  through  disintegration  of  the 
core  of  the  crystal.  Some  tourmalines  have  not  only  suffered  dis- 
integration, but  have  been  partly  or  entirely  removed,  leaving  only 
their  impressions  in  the  kaolin  which  formed  the  matrix. 

In  size  the  colored  tourmaline  crystals  differ  greatly,  ranging  from 
those  of  needle-like  dimensions  to  the  large  ones  described  below. 
Many  of  the  largest  are  compound. 

Anything  like  a complete  descriptive  list,  even  of  the  larger  and 
finer  tourmalines  found  at  Mount  Mica,  is  impracticable  in  this  report, 
but  a few  of  the  most  remarkable  will  be  briefly  described. 


a Penfield,  S.  F.,  On  cookeite  from  Paris  and  Hebron,  Me.:  Am.  Jour.  Sci.,  3d  ser.,  vol.  45,  pp.  393-396. 


90  PEGMATITES  AND  ASSOCIATED  ROCKS  OE  MAINE. 

The  largest  tourmaline  ever  found  at  Mount  Mica  came  from  the 
pocket  shown  in  Plate  IX,  B,  and  is  itself  figured  in  Plate  XIV.  It 
is  now  in  the  Paris  library,  to  which  it  has  been  loaned  by  Edward 
Hamlin,  of  Boston.  It  is  15J  inches  long,  7 inches  in  maximum 
breadth,  weighs  31  j pounds,  and  is  valued  at  not  less  than  $400. 
As  shown  in  the  plate,  the  base  is  fractured  so  that  the  crystal  is  now 
in  three  segments.  The  crystal  is  transparent  to  translucent  grass 
green  at  the  tip,  where,  too,  the  prism  faces  are  best  developed.  The 
middle  and  lower  flanks  of  the  terminal  segment  are  made  up  of  a 
mass  of  small  colorless  to  pale-pink  or  brownish  prisms  between  one- 
eighth  and  one-fourth  inch  in  diameter,  many  of  them  set  at  all  sorts 
of  angles  to  the  main  axis  of  the  compound  crystal.  A small  crystal 
of  white  quartz  about  2 inches  long  is  attached  to  the  side  of  this 
segment.  The  basal  segments,  which  are  about  4 inches  across,  show 
an  alternation  of  small  translucent  to  opaque  pink  and  green  prisms, 
the  colors  grading  into  one  another  parallel  to  the  prism  axes  and 
also  across  them. 

The  same  pocket  contained  another  compound  tourmaline  crystal, 
somewhat  similar  to  that  just  described  in  its  general  form  and  very 
similar  in  coloring,  but  smaller.  Its  length  is  about  10  inches,  its 
maximum  width  3J  inches,  and  its  weight  6^  pounds.  It  is  now  in 
the  possession  of  Mr.  Merrill. 

Besides  these  two  compound  crystals  the  pocket  yielded  two  simple 
crystals,  one  of  which  is  shown  in  Plate  XV  in  natural  size.  The 
upper  segment  of  this  is  in  Mr.  Merrill’s  possession,  the  lower  having 
been  cut  into  gems.  The  companion  crystal,  which  was  slightly 
smaller,  is  the  property  of  the  Hamlin  estate.  Both  crystals  are 
green  in  the  upper  part  and  pink  and  red  at  the  base.  They  are 
transparent  to  translucent,  and  the  segment  which  is  in  Mr.  MerrilFs 
possession  may  contain  some  gem  material  in  its  upper  portion. 
The  same  pocket  also  yielded  many  small  crystals  of  green  and  red, 
which  furnished  about  75  carats  of  cut  gems,  mostly  red  and  pink, 
but  some  green.  Three  nodules  of  colorless  tourmaline  were  also 
found,  one  of  which  would  cut  an  8-carat  stone.  Some  of  these  were 
remarkably  limpid  and  brilliant  when  cut.  In  all,  there  were  about 
75  pounds  of  tourmaline  crystals  in  this  pocket.  The  two  largest 
tourmaline  groups  and  most  of  the  others  lay  loose  in  the  disinte- 
grated clevelandite  and  cookeite  in  the  bottom  of  the  pocket.  No 
kaolin  was  present.  Lepidolite  occurred  around  the  walls  and 
across  the  bottom.  Many  quartz  crystals  lay  loose  in  the  bottom  of 
the  pocket,  the  upper  ones  having  the  apices  of  the  crystals  downward, 
showing  that  they  had  fallen  from  the  roof. 

A large  tourmaline,  consisting  of  a bundle  of  prisms  diverging 
slightly  toward  the  apex  of  the  crystal,  is  now  in  the  Cambridge 
Museum  of  Natural  History.  It  is  7 inches  long,  3J  inches  wide  near 


u. 


S.  GEOLOGICAL  SURVEY 


BULLETIN  445  PLATE  XV 


LARGE  SINGLE  CRYSTAL  OF  TOURMALINE  FROM  MOUNT  MICA.  NATURAL  SIZE. 
From  the  same  pocket  as  the  giant  tourmaline  shown  in  Plate  XIV. 


OXFORD  COUNTY. 


91 


the  apex,  and  2\  inches  wide  at  the  base.  Most  of  the  crystal  is  a 
deep  grass  green,  but  at  the  base  the  outer  green  layers  have  shelled 
off,  revealing  a cone  of  deep  pink,  which,  however,  does  not  appear 
to  penetrate  far.  The  base,  a nearly  straight  surface  inclined  about 
70°  to  the  main  prism  axis,  appears  to  be  a fracture  surface  and  is 
conchoidal.  It  is  partly  coated  with  cookeite,  as  are  the  lower  flanks 
of  the  prism,  showing  that  the  crystal  had  become  detached  from  its 
original  position  on  the  wall  of  the  pocket  before  the  cookeite  was 
deposited.  The  summit  terminations  are  not  crystal  faces,  but  are 
fracture  planes  standing  nearly  at  right  angles  to  the  main  axis.  The 
sides  are  closely  and  beautifully  striated.  The  crystal  is  transpar- 
ent to  translucent  and  does  not  appear  to  contain  any  gem  material. 
This  tourmaline  was  the  largest  found  in  the  giant  pocket  shown  in 
Plate  XIII.  It  lay  loose  in  the  bottom  in  a mass  of  kaolin  and  of 
cookeite  sand.  A few  other  smaller  tourmalines  were  found,  but 
none  were  of  gem  quality,  and  in  proportion  to  its  great  size  the 
pocket  was  remarkably  unproductive.  The  pocket  contained  large 
amounts  of  massive  and  crystal  quartz  plugged  full  of  small  opaque 
tourmaline  crystals.  In  one  end  there  was  about  a ton  of  the  pink 
kaolin  montmorillonite. 

The  largest  transparent  crystal  of  green  tourmaline  found  at  Mount 
Mica  was  discovered  by  Samuel  R.  Carter  in  1886  and  is  now  in  the 
Cambridge  Museum  of  Natural  History.  It  is  10  inches  in  length, 
2\  inches  in  diameter,  and  weighs  41  ounces.  Both  terminations 
have  been  preserved,  but  they  are  not  at  all  perfect.®  Although 
broken  into  four  pieces,  the  parts  have  been  easily  joined  by  cement. 
Its  middle  portion  would  probably  yield  some  fine  gems.  This 
crystal  came  from  an  unusually  large  pocket  4 feet  in  diameter,  along 
whose  sides  and  at  whose  bottom,  embedded  in  a sand  of  decom- 
posed cookeite,  lepidolite,  etc.,  were  found  fragments  of  certainly 
50  well-defined  tourmaline  crystals. 

The  most  remarkable  crystal  of  white  tourmaline  or  achroite 
found  at  this  locality  is  also  in  the  Cambridge  Museum  of  Natural 
History.  It  was  obtained  in  1869  from  a large  pocket  which  yielded 
several  other  crystals  of  smaller  size.  This  crystal  is  transparent, 
but  when  viewed  in  light  transmitted  at  right  angles  to  its  axis  appears 
smoky  toward  the  base;  when  viewed  along  the  axis  its  hue  is 
crimson.  Both  ends  are  tipped  with  green,  but  its  terminal  faces  are 
not  preserved.  Its  length  is  about  4 inches  and  its  width  1J  inches. 

The  finest  crystal  of  blue  tourmaline  or  indicolite  found  at  Mount 
Mica  is  in  the  Hamlin  cabinet.  It  is  transparent  throughout  its 
entire  shaft,  although  broken  into  five  parts.  Both  terminations  are 
preserved.  The  color,  when  viewed  at  right  angles  to  the  prism 


a Hamlin,  A.  C.,  The  history  of  Mount  Mica,  PI.  XXX  and  pp.  39-40. 


92 


PEGMATITES  AND  ASSOCIATED  ROCKS  OF  MAINE. 


length,  is  a beautiful  sapphire  blue,  changing  at  the  top  into  a deli- 
cate green.  It  is  about  4 inches  long  and  one-half  inch  in  diameter. 
It  is  illustrated  in  color  in  “The  history  of  Mount  Mica,”  Plate  XXVI. 

A remarkable  curved  crystal  of  gray  to  green  tourmaline,  trans- 
parent to  translucent  in  places,  was  found  in  1891,  and  is  now  in  the 
Carter  collection  in  the  public  library  at  Paris.  It  is  about  5 inches 
long  and  three-fourths  to  1 inch  in  diameter,  and  is  curved  through 
an  angle  of  about  20°. 

The  largest  flawless  gem  ever  cut  from  tourmaline  from  Mount 
Mica  weighs  69 1 carats  and  is  now  in  the  Tiffany  collection.  It  was 
part  of  a crystal  found  in  November,  1893,  and  was  sold  by  Merrill 
& Stone  for  $1,000.  The  crystal  from  which  it  came  is  described 
and  figured  in  “The  history  of  Mount  Mica,”  page  71  and  Plate 
XLIII.  It  yielded  a number  of  other  fine  gems,  one  of  which,  a 
pink  one,  weighed  18  carats. 

What  is  probably  the  largest  flawless  piece  of  transparent  tourma- 
line known  is  in  the  possession  of  L.  B.  Merrill,  its  finder,  the  present 
operator  of  the  Mount  Mica  mine.  In  its  uncut  condition  it  weighs 
411  carats.  It  formed  the  tip  of  a crystal  8 inches  long  and  1 inch 
in  diameter,  much  of  which  was  greatly  disintegrated. 

Beryl  occurs  principally  in  the  solid  pegmatite,  though  occasionally 
found  in  the  pockets.  The  varieties  found  in  the  solid  pegmatite  are 
mainly  pale  blue-green  and  opaque  or  translucent.  Certain  small 
portions  of  the  crystals  may  be  transparent,  and  from  these  some 
small  aquamarines  of  good  quality  have  been  cut.  One'  beryl  6 
inches  across,  observed  by  the  writer,  inclosed  both  muscovite  and 
black  tourmaline.  The  beryl  found  in  the  pockets  is  mostly  color- 
less to  pale  pink  caesium  beryl;  it  cuts  into  gems  which  in  artificial 
light  have  almost  the  beauty  of  diamonds.  It  is  apt  to  occur  in 
short,  button-shaped  prisms,  many  with  both  terminations  complete. 
Two  fine  specimens  of  caesium  beryl  are  in  the  Hamlin  collection  at 
the  Paris  public  library.  One  is  about  6 inches  in  diameter  and  1 
inch  high  and  has  three  sides  of  the  hexagonal  prism  perfect.  The 
other  is  about  6 inches  high,  shows  a good  basal  plane,  four  prism 
faces  quite  perfect  for  most  of  their  length,  and  two  pyramid  faces. 
These  crystals  are  only  in  small  part  transparent  and  are  much  flawed 
and  iron  stained  along  fractures. 

Production  and  method  of  mining. — It  is  impossible  accurately  to 
estimate  the  amount  and  value  of  material  for  gems  and  museum 
specimens  which  Mount  Mica  has  yielded,  but  Hamlin  in  his  history 
of  Mount  Mica  estimated  that  up  to  1895  the  locality  had  yielded 
more  than  100  tourmaline  crystals  which  would  be  considered 
unusually  fine  specimens  of  the  mineral,  besides  many  thousand 
smaller  crystals.  The  total  value  of  the  gems  and  cabinet  specimens 
which  have  been  taken  from  the  locality  up  to  the  present  day 
probably  exceeds  $50,000. 


OXFORD  COUNTY. 


93 


The  mine  is  worked  by  Merrill  & Stone,  the  drilling  being  done  by 
hand  and  the  blasting  with  black  powder,  so  as  to  run  as  little  risk 
as  possible  of  shattering  valuable  gem  material.  A derrick  operated 
by  a horse  windlass  is  used  in  transferring  the  waste  rock  to  the 
dump.  At  present  it  is  necessary  to  remove  a considerable  thick- 
ness of  schist  overlying  the  pocket-bearing  layer.  It  is  probable 
that  the  thickness  of  the  cover  rock  increases  southward,  and  that 
in  the  near  future  tunneling  will  be  found  the  most  economical  method 
of  working. 

PERU. 

The  pegmatites  of  Peru  were  studied  at  only  one  locality,  an  old 
mica  prospect  on  the  farm  of  J.  P.  York  near  the  central  part  of  the 
town.  The  mine  is  located  near  the  summit  of  the  southwest  slope 
of  a steep  hill  and  was  worked  only  in  the  summer  of  1902. 

The  whole  pegmatite  mass  is  hardly  over  150  feet  wide  on  the 
level  of  the  principal  openings  and  appears  to  have  the  form  of  an 
irregular  lens  elongate  in  a general  east-west  direction.  The  border- 
ing rock  is  a granite  gneiss  locally  very  rich  in  biotite.  The  openings 
are  below  the  crest  of  the  hill,  and  as  the  pegmatite  mass  is  traced 
eastward  toward  the  summit  it  is  found  to  be  associated  with  larger 
and  larger  amounts  of  granite  gneiss.  The  lowermost  exposures  on 
the  hill  slope  also  show  much  granite  gneiss  associated  with  the  peg- 
matite; the  latter  therefore  appears  to  pinch  out  rather  rapidly  both 
above  and  below,  and  consequently  to  be  of  rather  small  extent. 
The  trend  of  the  granite  gneiss  where  it  borders  the  pegmatite  on  the 
north  is  about  N.  70°  E.;  its  folia  dip  steeply  to  the  northwest. 

The  pegmatite  varies  greatly  in  coarseness  from  point  to  point. 
Its  dominant  components  are  orthoclase-microcline,  quartz,  mus- 
covite, and  biotite.  A few  feldspar  crystals  are  3 feet  across,  but  for 
the  most  part  this  mineral  is  so  intimately  mixed  with  biotite  as  to  be 
commercially  valueless.  Locally  the  biotite  forms  blades  4 to  5 feet 
long  and  2 to  3 inches  wide.  Some  crystals  show  muscovite  surround- 
ing biotite  in  parallel  growth.  No  muscovite  books  more  than  3 to  4 
inches  across  were  seen  either  in  the  solid  pegmatite  or  in  the  dump 
piles  of  the  mine,  and  specimens  preserved  at  a neighboring  farm- 
house and  said  to  be  as  good  as  any  of  the  mica  obtained  would  none 
of  them  cut  pieces  of  clear  mica  measuring  more  than  2 by  3 inches. 
There  is  no  distinct  vein  particularly  rich  in  muscovite  and  the  prop- 
erty can  not  be  regarded  as  a commercial  proposition  for  mica 
mining. 

RUMFORD. 

The  town  of  Rumford  is  occupied  by  quartz-mica  schists,  intruded 
and  in  some  places  intimately  injected  by  granite  and  pegmatite. 
The  relations  at  a number  of  localities  throw  light  on  the  genesis  of 
the  rock  concerned. 


94  PEGMATITES  AND  ASSOCIATED  ROCKS  OF  MAINE. 

Vicinity  of  Rumford  Falls. — The  exposures  examined  were  on  the 
east  shore  of  Androscoggin  River  at  the  falls,  a mile  or  so  above 
Rumford  Falls  village.  The  schists  are  dark  gray  to  purplish  on 
the  fresh  surfaces  and  purplish  to  rusty  brown  on  the  weathered 
surfaces.  They  are  garnetiferous  quartz-mica  schists  and  strike  N. 
30°  to  40°  W.,  with  dips  of  20°  to  30°  NE.  The  schists  are  intruded 
by  sills  and  dikes  of  fine-grained  gray  granite,  by  pegmatite,  and  by 
small  quartz  veins. 

An  instructive  contact  between  the  schist  and  pegmatite  is  shown 
in  Plate  X,  B,  and  has  already  been  described  on  pages  34. 

Another  intrusive  mass  in  the  schists  is  of  irregular  sill-like  form, 
and  consists  partly  of  biotite  granite  and  partly  of  pegmatite.  It  is 
interesting  because  of  gradual  and  complete  gradation  between 
granite  and  pegmatite.  The  biotite  granite  is  gray  in  color  with  an 
average  size  of  grain  of  not  over  1 millimeter.  The  pegmatite  in 
addition  to  quartz  and  feldspar  shows  muscovite,  but  very  little 
biotite. 

A number  of  small  dikes  of  fine-grained  granite  intrude  the  schists 
at  this  locality,  both  parallel  to  and  transverse  to  the  trend  of  the 
latter.  All  of  these  are  characterized  by  sharp  parallel  walls  and 
are  in  great  contrast  to  the  pegmatite  dikes  which  traverse  the  same 
schists  but  are  characterized  by  wavy  and  irregular  forms,  the  two 
sides  of  the  dike  or  sill  in  few  places  being  parallel.  The  intrusion 
of  the  schist  by  the  fine-grained  granite  in  the  railroad  cut  opposite 
the  falls  is  so  intimate  that  a dike  network  results. 

Microscopic  comparisons  were  made  between  the  medium-grained 
granite  of  this  locality  and  the  pegmatite  of  an  irregular  dike  cutting 
the  granite.  The  dike  is  exposed  for  20  feet  and  is  1 foot  wide  at  its 
base,  but  broadens  upward  within  2 feet  to  a width  of  4 feet,  thence 
narrowing  again  within  a few  feet  to  a width  of  1 foot.  There  is 
complete  crystallographic  continuity  between  the  two  rocks  at  their 
contact,  but  the  transition  from  one  to  the  other  is  usually  complete 
in  a space  of  one-fourth  to  one-half  inch.  The  minerals  character- 
istic of  the  two  rocks  are  identical. 

The  granite  shows  considerable  and  irregular  variations  in  color, 
due  to  differences  in  the  abundance  of  biotite.  Few  of  its  mineral 
grains  exceed  one-eightli  inch,  and  their  average  size  is  about  one- 
sixteenth.  Its  dominant  minerals  are  quartz,  orthoclase  and  micro- 
cline,  oligoclase  (extinction  angles  up  to  13°;  refractive  index  about 
equal  to  balsam),  and  biotite.  Garnet  and  muscovite  are  subordinate 
accessories.  Oligoclase  appears  to  be  only  slightly  less  abundant 
than  the  potash  feldspars.  Small  quartzes  of  rounded  cross  section 
and  a few  with  hexagonal  outlines  (some  with  corners  rounded)  are 
inclosed  by  orthoclase,  microcline,  or  other  quartz.  A few  small  biotite 
laths  are  wholly  inclosed  by  oligoclase,  and  a few  rounded  crystals 


OXFORD  COUNTY. 


95 


of  oligoclase  are  inclosed  by  orthoclase.  These  relations  point  to  the 
existence  in  the  magma  of  small  crystals  of  quartz,  biotite,  and 
oligoclase  not  long  before  the  bulk  of  the  rock  crystallized.  A few 
small  areas  show  an  intergrowth,  more  or  less  graphic  in  pattern, 
of  quartz  with  oligoclase  or  microcline. 

The  minerals  of  the  pegmatite  are  identical  with  those  of  the 
granite,  but  form  much  larger  crystals  and  exhibit  markedly  greater 
diversity  in  the  size  of  the  mineral  grains.  Microcline  is  the  dominant 
feldspar,  and  much  of  it  is  perthitically  intergrown  with  plagioclase, 
which  appears  to  be  albite-oligoclase  in  composition.  The  same 
plagioclase  also  forms  separate  crystal  grains,  usually  much  smaller 
than  those  of  microcline.  Biotite  is  abundant  and  has  altered  some- 
what to  chlorite.  In  a few  places  quartz  is  micrographically  inter- 
grown with  the  plagioclase.  Many  small  quartzes  of  rounded  out- 
line or  showing  hexagonal  forms  with  rounded  corners  are  inclosed 
by  the  microcline.  Muscovite  is  rare. 

The  mineralogical  similarity  of  these  two  rocks  even  as  regards 
the  composition  of  the  plagioclase,  and  the  presence  in  both  of  small 
quartzes  of  an  earlier  crystallization  inclosed  by  later  feldspar,  taken 
in  connection  with  their  close  field  association,  suggest  their  deriva- 
tion from  the  same  magmatic  source. 

Black  Mountain  mica  mine. — A mine  which  has  been  operated  for 
scrap  mica  by  Oliver  Gildersleeve,  of  Gildersleeve,  Conn.,  is  located 
on  Black  Mountain  in  the  northern  part  of  the  town  of  Rumford. 
The  two  quarry  pits  are  hillside  excavations  about  two-thirds  of  the 
way  up  the  mountain  on  its  western  slope  and  are  about  three- 
fourths  of  a mile  from  the  road  between  North  Rumford  and  Rox- 
bury  Notch.  The  upper  pit  is  about  200  feet  long,  50  feet  wide, 
and  25  feet  in  greatest  depth.  Another  just  below  it  on  the  slope  is 
about  100  feet  wide,  100  feet  long,  and  35  feet  in  maximum  depth. 

The  rock  at  these  pits  is  an  exceedingly  coarse  pegmatite  which 
is  intrusive  in  an  irregular  manner  in  metamorphosed  sediments 
trending  N.  30°  to  40°  W.  and  dipping  70°  to  80°  NE.  The  latter 
are  slightly  contorted  but  reveal  their  sedimentary  origin  through 
an  alternation  of  quartzitic  and  more  shaly  beds. 

The  pegmatite  here  shows  some  characters  which  differentiate  it 
from  any  of  the  other  deposits  studied,  though  in  general  its  char- 
acters approach  more  closely  to  the  pegmatite  of  the  gem- tourmaline 
localities  than  to  that  of  the  other  mica  prospects  in  the  State. 
Potash  feldspar  is  almost  entirely  absent,  the  dominant  feldspar 
being  albite  of  the  bladed  clevelandite  variety.  Muscovite  is  the 
mineral  next  in  abundance,  constituting  about  30  to  40  per  cent  of 
the  whole  deposit.  Locally,  however,  it  forms  three-fourths  of  the 
pegmatite  mass.  The  largest  crystal  of  mica  seen  by  the  writer  was 
li  feet  wide  and  3 feet  long,  but  blade-shaped  or  spearhead-shaped 


96  PEGMATITES  AND  ASSOCIATED  ROCKS  OF  MAINE. 

crystals,  1 to  2 feet  long,  are  very  common.  Some  masses  weighing 
half  a ton  are  almost  purely  mica.  All  of  the  mica  shows  one  or 
more  of  the  defects  known  as  twinning,  wedge  structure,  and  ruling. 
None  of  it  will  yield  any  plate  mica.  Several  of  the  mica  books  ob- 
served were  1 foot  thick  (at  right  angles  to  the  cleavage).  Near  the 
walls  of  the  pegmatite  mass  the  mica  books  tend  to  orient  themselves 
with  their  long  axes  perpendicular  to  the  contact,  though  only  within 
6 inches  or  so  of  the  wall  is  there  any  noticeable  decrease  in  the  coarse- 
ness of  the  pegmatite.  The  quartz  of  this  pegmatite  is  mostly  opaque 
but  is  pure  white.  Spodumene  is  unusually  abundant  in  long  flat 
crystals,  some  of  them  2£  feet  long  and  3 to  4 inches  thick.  The 
color  is  light  gray  to  white.  Some  of  the  spodumene  is  intimately 
intergrown  with  quartz. 

A remarkable  feature  of  this  deposit  is  the  presence  in  the  peg- 
matite of  irregular  masses  of  medium-grained  granite,  which  in  some 
parts  consists  of  muscovite,  quartz,  and  plagioclase,  and  along  cer- 
tain bands  or  irregular  bunches  is  one-third  to  one-half  bright  pink 
tourmaline,  producing  a stone  of  considerable  beauty.  Under  the 
microscope  the  principal  minerals  are  seen  to  be  quartz,  muscovite, 
pink  tourmaline,  and  basic  oligoclase  (extinction  angles  up  to  17°; 
refractive  index  near  balsam).  In  the  thin  section  only  very  faint 
pleochroism  is  seen  in  the  tourmaline.  Tourmaline  constitutes  the 
largest  crystals  in  the  rock  and  shows  a tendency  toward  the  devel- 
opment of  radiate  bundles,  one-eighth  to  one-fourth  inch  across, 
made  up  of  small  prisms.  The  average  size  of  grain,  exclusive  of  the 
tourmaline  crystals,  is  from  0.3  to  0.6  millimeter.  This  granite  is 
plainly  a crystallization  from  the  pegmatite  magma  and,  like  the 
pegmatite,  numbers  quartz,  muscovite,  and  pink  tourmaline  among 
its  chief  constituents.  Many  large  spodumene  crystals  are  embedded 
in  this  tourmaline  granite.  Its  quantity  and  uniformity  are  not 
sufficient  to  give  it  any  commercial  importance. 

In  the  pegmatite,  greenish-black  tourmaline  occurs  in  crystals 
averaging  one-half  inch  to  1J  inches  in  diameter  and  4 to  8 inches  in 
length.  They  are  commonly  associated  with  quartz  or  clevelandite 
and  only  rarely  are  in  contact  with  muscovite,  being  rare  in  the  more 
micaceous  parts  of  the  pegmatite.  Pink  to  gray  opaque  tourmaline 
also  occurs,  generally  surrounded  by  quartz.  One  aggregate  exposed 
in  a loose  quartz  fragment  is  7 inches  long.  It  is  a brush-shaped 
aggregate  of  tourmaline  crystals  and  enlarges  from  a diameter  of 
about  2J  inches  at  the  base  to  about  4 inches  at  the  top,  the  cross 
section  being  nearly  circular. 

Most  of  the  schist  exposed  near  this  mine  is  somewhat  weathered. 
Noticeable  contact  metamorphism,  though  confined  to  the  immediate 
vicinity  of  the  pegmatite,  has  been  more  severe  than  along  most  of 


OXFORD  COUNTY. 


97 


the  pegmatite  contacts  studied.  It  has  resulted  in  the  abundant 
development  of  prisms  of  cinnamon-brown  tourmaline  from  one- 
fourth  to  one-half  inch  long  and  one-sixteenth  to  one-eightli  inch  in 
diameter  in  certain  of  the  more  muscovitic  layers.  More  biotitic 
portions  present  a mottled  appearance,  due  to  the  occurrence  of  the 
biotite  in  irregular  aggregates  one-eighth  to  one-fourth  inch  in 
diameter.  Under  the  microscope  this  mottled  rock  is  seen  to  con- 
sist of  brown  biotite,  light-green  hornblende,  quartz,  labradorite, 
titanite,  magnetite,  and  apatite,  the  latter  in  small  hexagonal  prisms 
filled  with  a cloud  of  very  minute  inclusions.  The  tendency  to  ag- 
gregation of  the  biotite,  hornblende,  titanite,  and  magnetite  gives 
the  mottled  appearance,  the  white  intervening  areas  being  largely 
quartz  and  labradorite.  The  mineral  grains  of  this  rock  are  inter- 
locking and  the  texture  granular  and  indistinguishable  from  that 
of  an  igneous  rock.  Field  relations  show,  however,  that  the  rock 
is  a phase  of  the  sedimentary  schist  wall  rock  which  has  undergone 
complete  recrystallization. 

It  is  notable  that  neither  of  the  metamorphosed  phases  of  the 
wall  rock  described  above  contains  any  minerals  except  the  common 
ones,  quartz  and  muscovite,  that  are  characteristic  of  the  neigh- 
boring pegmatite.  The  tourmaline  of  the  schist  is  brown  and  wholly 
dissimilar  from  any  found  in  this  or  any  other  pegmatite  of  the 
State.  Additions,  if  any,  received  by  the  wall  rock  from  the  peg- 
matite during  the  complete  recrystallization  of  the  former  were  ionic 
in  their  character,  the  minerals  characteristic  of  the  pegmatite,  with 
the  possible  exception  of  quartz,  not  being  added  as  such  to  the 
intruded  rock. 

The  quarry  was  opened  in  about  1901  by  Oliver  Gildersleeve  and 
has  been  worked  for  four  seasons.  About  250  tons  of  mica  is 
reported  to  have  been  mined  in  1905.  The  quarry  was  idle  through- 
out 1906,  in  which  year  the  writer  visited  it,  and  so  far  as  is  known  has 
not  reopened  since.  Steam  drills  were  employed  and  sheds  built 
for  hand  picking  the  mica,  which  was  packed  in  100-pound  bags  and 
hauled  by  team  7 miles  to  Frye,  on  the  Rangeley  division  of  the 
Maine  Central  Railroad.  From  Frye  it  was  shipped  to  a grinding 
mill  at  Gildersleeve,  Conn.  About  1,000  tons  in  all  are  reported  to 
have  been  shipped.  The  quantity  of  scrap  mica  still  available  at 
this  quarry  is  large,  but  there  is  no  plate  mica,  nor  is  it  probable  that 
further  excavation  will  disclose  any.  It  is  doubtful  if  at  present  the 
property  can  be  profitably  exploited  for  scrap  mica  in  view  of  the 
fact  that  the  refuse  cuttings  from  plate  mica  properties  appear  able 
to  meet  entirely  the  present  demand  for  scrap  mica. 

63096°— Bull.  445—11 7 


98  ’ PEGMATITES  AND  ASSOCIATED  ROCKS  OF  MAINE. 

STANDISH. 

The  rocks  of  Standish  were  studied  only  in  the  western  part  of  the 
town,  in  the  Spence  Hills,  which  lie  about  5 miles  north-northeast 
of  Paris  village.  The  rocks  are  schists  of  the  same  metamorphic- 
sedimentary  type  observed  in  the  town  of  Paris,  and  are  rather  flat 
lying.  As  in  Paris,  they  are  intruded  by  granite  and  pegmatite,  but 
these  rocks  are  much  less  abundant  than  at  most  places  in  Paris,  and 
large  masses  of  the  schist  are  wholly  free  from  granitic  material  of 
any  kind. 

The  collection  of  the  Sheffield  Scientific  School  of  Yale  University 
contains  several  fine  crystals  of  columbite  from  the  pegmatites  of 
this  town. 

STONEHAM. 

GEOLOGY. 

The  rocks  of  the  town  of  Stoneham  are  almost  exclusively  gneisses 
intruded  by  pegmatite  and  granite,  the  igneous  rocks  being  on  the 
whole  more  abundant  than  in  most  of  the  towns  to  the  east. 

Excellent  exposures  on  the  south  shore  of  Keewaydin  Lake  (Lower 
Stone  Pond),  near  the  village  of  East  Stoneham,  show  rather  fine- 
grained pegmatite  intruding  a purplish-gray  gneiss,  indistinguishable 
in  the  field  from  certain  gneisses  exposed  at  the  Auburn  reservoir 
site  on  Goff  Hill.  This  rock  is  a quartz-feldspar-muscovite-biotite 
schist  whose  origin  can  not  be  definitely  stated.  It  closely  resembles 
many  phases  of  the  sedimentary  schists  which  have  been  intensely 
injected  by  pegmatite  and  may  be  of  similar  origin.  Both  schist 
and  pegmatite  are  intruded  at  “ Striped  ledge/’  on  this  lake,  by  a 
remarkable  dike  network  of  fine-grained  diabase.  (See  PI.  XVI,  A.) 

Granite  found  a few  miles  west  of  Keewaydin  Lake,  in  the  bed  of 
a creek  flowing  into  Upper  Kezar  Lake,  is  a millimeter-grained,  light- 
gray  rock,  in  which  a faint  gneissic  habit  is  recognizable,  due  to  the 
occurrence  of  biotite  in  slightly  greater  abundance  along  certain 
vaguely  defined  bands  than  along  others.  The  microscope  shows  its 
minerals  to  be  quartz,  albite,  biotite  (partly  altered  to  chlorite),  and 
a little  muscovite.  The  rock  differs  from  most  of  the  granites  of 
Maine  in  being  a soda  granite,  potash  feldspar  being  apparently 
wholly  absent.  The  microscopic  texture  is  typically  granitic. 

GEM  LOCALITIES. 

Pegmatites  have  not  been  systematically  worked  at  any  place  in 
this  town  but  have  yielded  to  prospectors  and  mineral  collectors  a 
large  number  of  beryls,  some  of  which  are  among  the  finest  of  their 
kind,  and  also  fine  specimens  of  topaz,  amethyst,  beryllonite,  and 
other  minerals.  Some  of  the  finest  of  these  specimens  have  been 
obtained  from  localities  which  can  not  now  be  identified. 


U.  S.  GEOLOGICAL  SURVEY 


BULLETIN  445  PLATE  XVI 


A.  NETWORK  OF  DIABASE  DIKES  CUTTING  PEGMATITE  AND  ASSOCIATED  GNEISS  AT 
KEEWAYDIN  LAKE,  IN  STONEHAM. 


B.  QUARTZ  DIKE  CUTTING  PEGMATITE  AT  HOWE  QUARRY,  SOUTH  GLASTONBURY,  CONN. 

Showing  light-colored  feldspar  crystals  with  well-developed  crystal  faces  projecting  into  the  quartz  of  the 
dike.  The  quartz  appears  dark  in  the  photograph. 


OXFORD  COUNTY. 


99 


Sugar  Hill. — Two  fine  aquamarines,  found  near  Sugar  Hill,  in  the 
western  part  of  Stoneham,  are  described  as  follows  by  Kunz:  a 

The  writer  obtained  at  Stoneham,  Oxford  County,  Me.,  two  beryls,  exceptional  for 
the  United  States.  These  were  found  in  1881,  several  miles  apart  and  several  miles 
from  the  topaz  region,  by  farmers  who  were  traversing  pastures  in  the  township. 
The  first  was  found  in  two  pieces,  as  if  it  had  been  roughly  used,  and  broken,  and 
discarded  as  worthless,  or  else  broken  in  taking  from  the  rock  and  then  rejected,  its 
value  not  being  known.  This  crystal  measured  4|  inches  (120  millimeters)  long  and 
2t1o  inches  (54  millimeters)  wide,  and  was  originally  about  5 inches  (130  millimeters) 
long  and  3 inches  (75  millimeters)  wide.  The  color  was  rich  sea  green  viewed  in 
the  direction  of  the  longer  axis  of  the  prism,  and  sea  blue  of  a very  deep  tint  through 
the  side  of  the  crystal.  In  color  and  material  this  is  the  finest  specimen  that  has 
been  found  at  any  North  American  locality,  and  the  crystals,  unbroken,  would  equal 
the  finest  foreign  crystals  known.  It  furnished  the  finest  aquamarine  ever  found  in 
the  United  States,  measuring  If  inches  (35  millimeters)  by  If  inches  (35  millimeters) 
by  three-fourths  inch  (20  millimeters).  It  was  cut  as  a brilliant  and  weighs  133f 
carats.  The  color  is  bluish  green,  and,  with  the  exception  of  a few  hair-like  internal 
striations,  is  perfect.  In  addition  to  this  remarkable  gem,  the  same  crystal  furnished 
over  300  carats  of  fine  stones. 

The  other  crystal  is  doubly  terminated,  being  If  inches  (41  millimeters)  long  and 
f inch  (15  millimeters)  in  diameter.  Half  of  it  is  transparent,  with  a faint  green 
color;  the  remainder  is  of  a milky  green  and  only  translucent. 

The  large  133-carat  gem  cut  from  the  first  of  these  two  crystals  is 
now  in  the  possession  of  the  Field  Museum  of  Natural  History  at 
Chicago. 

Fine  crystals  of  golden  beryl  have  been  obtained  at  Edgecomb 
Mountain  in  Stoneham. 

On  the  south  flank  of  Sugar  Hill  a ledge  of  coarse  pegmatite  has 
yielded  a number  of  fine  transparent  beryls.  The  pegmatite  mass 
here  appears  to  be  rather  flat  lying  and,  as  exposed  in  a near-by 
vertical  face,  is  at  least  15  feet  in  thickness;  it  can  be  followed  for 
100  feet  or  so  along  the  hillside.  The  buff-colored  potash  feldspar 
of  this  ledge  forms  large  enough  crystals  and  is  sufficiently  free  from 
iron-bearing  minerals  to  be  of  commercial  grade  for  pottery  purposes, 
but  its  distance  from  the  railroad  would  render  its  exploitation 
unprofitable  at  the  present  time. 

Crystals  of  beryllonite,  a phosphate  of  beryllium  and  sodium,  have 
been  found  in  western  Stoneham  on  the  farm  of  Eldin  McAllister,  on 
the  south  side  of  Sugar  Hill,  a few  rods  below  the  beryl  locality  just 
described.  When  visited  by  the  writer,  in  September,  1906,  the  only 
opening  consisted  of  a small  pit  dug  in  the  talus  and  glacial  drift 
near  the  foot  of  the  hill.  The  soil  in  which  the  beryllonite  crystals 
were  found  contains  also  fragments  of  quartz,  feldspar,  and  mica,  and 
a few  of  apatite,  beryl,  cassiterite,  columbite,  and  triplite.  Some  of 
the  beryllonite  crystals  themselves  are  attached  to  apatite  and  some 
retain  what  appear  to  be  the  impressions  of  muscovite  crystals. 
There  can  be  little  doubt  therefore  that  the  beryllonite  occurred 


a Kunz,  G.  F.,  Gems  and  precious  stones,  pp.  92-93. 


100 


PEGMATITES  AND  ASSOCIATED  ROCKS  OF  MAINE. 


as  a constituent  of  a pegmatite  mass,  and  it  probably  occurred  in 
pockets.  The  minerals  were  probably  dislodged,  by  the  action  of 
glacial  ice,  from  a decomposed  pegmatite  ledge  somewhere  on  the 
flanks  of  Sugar  Hill  and  were  subsequently  deposited  in  their  present 
position  at  the  base  of  the  hill.  Prospecting  on  the  hill  northwest 
of  the  beryllonite  locality  may  eventually  disclose  the  source. 

The  locality  was  first  worked  by  E.  D.  Andrews,  of  Albany,  who, 
in  searching  for  smoky  quartz,  found  an  unknown  mineral,  which  was 
later  identified  by  E.  S.  Dana  in  1888  as  a new  species  and  called 
beryllonite.  Its  mineral  characters  have  been  fully  described  by 
Dana  and  Wells. a 

Ilarndon  Hill . — A well-known  topaz  locality  is  located  on  the  sum- 
mit of  Harndon  Hill,  in  the  southwestern  corner  of  the  town  of  Stone- 
ham,  within  one-fourth  mile  of  the  Stow  line.  It  was  opened  in  the 
early  eighties  by  Nathan  H.  Perry,  of  South  Paris,  and  worked  inter- 
mittently for  a number  of  years,  but  at  the  time  of  the  writer’s  visit 
in  September,  1906,  had  been  practically  idle  for  over  ten  years. 
The  workings  consist  of  several  openings  close  together,  a few  feet 
across  and  2 or  3 feet  in  depth,  in  the  coarse  pegmatite  which  caps 
the  hill  at  this  point. 

The  locality  has  been  visited  by  George  F.  Kunz,  of  New  York, 
and  its  minerals  described  by  him.6  lie  describes  the  character  and 
mode  of  occurrence  of  the  topaz  as  follows: 

This  locality  is  the  first  in  New  England  that  has  furnished  good,  clear,  and  dis- 
tinct crystals  of  topaz,  and  thus  far  it  has  produced  the  best  crystals  found  in  the 
United  States.  Of  these  crystals,  nearly  all  the  finest  were  found  in  one  pocket  in 
clevelandite  (lamellar  albite)  at  its  junction  with  a vein  of  margarodite  (hydromica) 
and  one  was  entirely  surrounded  by  clevelandite.  The  finest  crystals  vary  in  size 
from  10  millimeters  to  the  largest,  which  measures  transversely  60  by  65  millimeters 
and  vertically  56  millimeters.  They  are  transparent  in  parts,  and  contain  cavities 
of  fluids,  the  nature  of  which  has  not  yet  been  determined.  A few  small  perfect 
gems  have  been  cut  from  the  fragments  of  a large  crystal  that  was  broken. 

The  finest  crystals  are  colorless  or  faintly  tinted  with  green  or  blue.  Some  opaque 
crystals  are  as  much  as  300  millimeters  across  the  largest  part  and  weigh  from  10  to  20 
kilograms  each.  They  are  not  perfect  in  form,  the  faces  are  rough,  and  generally  they 
were  broken  before  they  were  taken  from  the  rock.  The  color  in  these  rough  crystals 
is  more  decided  than  in  the  finer  ones  and  is  a light  shade  of  either  green,  yellow,  or 
blue.  The  specific  gravity  of  the  transparent  material  is  3.54,  and  the  hardness  the 
same  as  that  of  the  yellow  topaz  from  Ouro  Preto  (formerly  Villa  Rica),  Brazil. 

The  properties  of  this  topaz  have  been  further  discussed  by  Pen- 
field  and  Minor; c its  chemical  composition  has  been  studied  and  its 
alteration  to  damourite  has  been  described  by  Clarke  and  Diller.d 
No  topaz  was  visible  at  the  time  of  the  writer’s  visit. 

aDana,  E.  S.,  and  Wells,  H.  L.,  Am.  Jour.  Sci.,  3d  ser.,  vol.  37,  1889,  pp.  23-32. 

bKunz,  G.  F.,  Topaz  and  associated  minerals  at  Stoneham,  Me.:  Am.  Jour.  Sci.,  3d  ser.,  vol.  27,  1884, 

pp.  212-216. 

cPenfield,  S.  I.,  and  Minor,  J.  C.,  jr.,  On  the  chemical  composition  and  related  physical  properties  ol 
topaz:  Am.  Jour.  Sci.,  3d  ser.,  vol.  47,  1894,  p.  390. 

^Clarke,  F.  W.,  and  Diller,  J.  S.,  Topaz  from  Stoneham,  Me.:  Am.  Jour.  Sci.,  3d  ser.,  vol.  29,  1885, 
pp.  378-384. 


OXFORD  COUNTY. 


101 


Other  constituents  of  the  pegmatite  at  this  locality  are  the  follow- 
ing, the  descriptions  being  partly  those  of  Kunz: 

1.  Apatite  occurs  in  the  cavities  as  small  doubly- terminated  crys- 
tals and  in  the  solid  pegmatite  as  opaque  vitreous-green  masses 
weighing  up  to  2 pounds. 

2.  Beryl  occurs  in  large  colorless  to  pale-green  crystals  embedded 
in  the  solid  pegmatite.  Most  of  them  are  opaque  to  translucent  with 
small  colorless  transparent  portions.  Kunz  reports  that  one  band 
unusually  rich  in  beryl  was  traced  for  nearly  40  feet.  Some  of  the 
crystals  in  this  band  were  about  a yard  long  and  over  a foot  across. 

3.  Clevelandite  in  white  plates  is  very  abundant,  as  in  most  of  the 
gem-bearing  pegmatites.  It  occurs  in  particular  abundance  and  per- 
fection of  crystal  form  on  the  walls  of  the  pockets. 

4.  Columbite  is  usually  associated  with  clevelandite,  lying  either 
on  crystals  of  the  latter  in  cavities  or  else  between  the  plates  of  it. 
Its  crystals  vary  in  length  from  1 to  10  millimeters  and  are  not  very 
perfect.  One  pocket  afforded  over  40  pounds  of  pure  material,  and 
one  mass  which  seemed  to  have  belonged  to  a single  crystal  group 
weighed  over  17  pounds. 

5.  Fluorite  fills  small  cavities  in  the  clevelandite.  The  masses  are 
rarely  over  10  millimeters  across  and  the  color  is  very  deep  purple. 
A number  of  very  minute  octahedra  resembling  blue  topaz  have  been 
found. 

6.  The  pink  kaolin  montmorillonite  occurs,  according  to  Kunz,  in 
masses  that  range  in  color  from  a very  delicate  pink  to  tints  closely 
approximating  red,  filling  the  cavities  and  interstices  in  the  cleve- 
landite. It  also  occurs  in  botryoidal  masses  resembling  rliodochro- 
site,  on  crystals  of  clevelandite. 

7.  Triplite  is  scattered  irregularly  through  the  solid  pegmatite  in 
masses  usually  under  2 pounds  in  weight,  though  one  mass  broken 
out  in  the  blasting  furnished  over  100  pounds  of  rather  pure  material. 

8.  Herderite,  in  short  prisms  from  1 millimeter  to  1 centimeter  long, 
occurs  in  the  topaz-bearing  pockets  and  has  been  described  by  Hid- 
den and  Mackintosh  a and  further  discussed  by  Dana  6 and  Penfield.6 

9.  Bertrandite  occurs  in  the  pockets  with  herderite  and  topaz.  It 
has  been  described  by  Penfield.^ 

10.  A single  occurrence  of  hamlinite  has  been  noted  at  this  locality. 
The  mineral  formed  minute  rhombohedral  crystals  attached  to  herd- 
erite, margarodite,  muscovite,  and  feldspar,  and  associated  with  ber- 

a Hidden,  W.  E.,  On  the  probable  occurrence  of  herderite  in  Maine:  Am.  Jour.  Sci.,  3d  ser.,  vol.  27, 1884, 
p.  73.  Hidden,  W.  E.,  and  Mackintosh,  J.  B.,  On  herderite,  a glucinum  calcium  phosphate  and  fluoride 
from  Oxford  County,  Me.:  Idem,  pp.  135-138. 

b Dana,  E.  S.,  On  the  crystalline  form  of  the  supposed  herderite  from  Stoneham,  Me.:  Idem,  pp. 
229-232. 

cPenfield,  S.  L.,  On  the  crystallization  of  herderite:  Am.  Jour.  Sci.,  3d  ser.,  vol.  47,  1894,  pp.  333-336. 

d Penfield,  S.  L.,  Crystallized  bertrandite  from  Stoneham,  Me.,  and  Mount  Antero,  Colorado:  Am. 
Jour.  Sci.,  3d  ser.,  vol.  37,  1889,  pp.  213-215;  Note  concerning  bertrandite  crystals  from  Oxford  County, 
Me. : Idem,  4th  ser.,  vol.  4,  1897,  p.  316. 


102 


PEGMATITES  AND  ASSOCIATED  ROCKS  OF  MAINE. 


trandite.  It  was  named  in  honor  of  A.  C.  Hamlin,  of  Bangor,  who  for 
many  years  developed  the  famous  tourmaline  mine  at  Mount  Mica. 
The  mineral  has  been  described  by  Hidden  and  Penfield.0 

Other  minerals  from  this  locality  are  autunite,  biotite,  gehlenite, 
garnet,  muscovite,  quartz,  triphylite,  and  zircon. 

STOW. 

The  rocks  of  the  town  of  Stow,  so  far  as  seen  by  the  writer,  are  all 
granitic;  they  include  pegmatite,  normal  granite,  and  granite  gneiss. 

Amethystine  quartz  has  been  obtained  on  Deer  Hill  near  the  New 
Hampshire  line.  When  visited  by  the  writer  in  September,  1906,  the 
only  openings  observed  were  a number  of  shallow  pits  dug  in  the  soil 
on  the  southeastern  slope  of  the  hill.  The  amethyst  crystals  occur 
loose  in  this  soil  or  attached  to  loose  fragments  of  feldspar.  The 
small  pieces  found  by  the  writer  were  all  of  a very  pale  lavender  tint 
and  in  most  of  them  the  color  was  very  unevenly  distributed.  The 
amethyst  was  probably  derived  from  pockets  in  the  pegmatite,  but 
so  far  as  known  the  ledge  has  not  been  opened.  The  whole  summit 
of  the  hill  is  composed  of  pegmatite  of  the  type  usual  in  western  Maine. 
Certain  portions  are  coarse  enough  and  sufficiently  free  from  iron- 
bearing minerals  to  be  of  commercial  grade  for  pottery  purposes,  but 
their  quantity  is  small. 

The  characters  of  the  rocks  are  well  shown  in  the  bed  of  Great 
River  near  the  road  bridge  just  southwest  of  Deer  Hill,  where  the 
principal  rock  is  a rather  fine-grained  biotite-muscovite  granite,  in 
part  massive,  but  mostly  of  gneissic  texture.  This  is  crossed  by  an 
irregular  band  of  muscovite-biotite  pegmatite,  which  ranges  from  6 
inches  to  2 feet  in  width ; it  is  without  sharp  walls  and  grades  imper- 
ceptibly into  the  granite  gneiss.  The  mineralogic  similarity  and  the 
gradation  from  one  rock  into  the  other  indicate  a common  magmatic 
source.  The  pegmatite  appears  to  have  been  intruded  before  the 
complete  solidification  of  the  granite. 

From  Deer  Hill  southward  to  Stow  village  the  rocks  are  pegmatite 
and  fine-grained  granite.  From  Stow  village  to  Lovell  village  the 
bed  rock  near  the  roads  is  obscured  by  extensive  glacial  outwash 
deposits  of  sand. 

WATERFORD. 

The  rocks  of  Waterford,  so  far  as  seen  by  the  writer,  are  largely 
granites  and  associated  pegmatite,  though  some  schist  of  probable 
sedimentary  origin  is  found  in  the  eastern  part  of  the  town.  The 
pegmatite  at  two  localities  has  in  the  past  been  worked  for  mica. 

a Hidden,  W.  E.,  and  Penfield,  S.  L.,  On  hamlinite,  a new  rhombohedral  mineral  from  the  herderite 
locality  at  Stoneham,  Me.:  Am.  Jour.  Sci.,  3d  ser.,  vol.  39,  1890,  pp.  511-513.  Penfield,  S.  L.,  On  the 
chemical  composition  of  hamlinite  and  its  occurrence  with  bertrandite  at  Oxford  County,  Me.:  Am.  Jour. 
Sci.,  4th  ser.,  vol.  4, 1897,  pp.  313-316. 


OXFORD  COUNTY. 


103 


South  Waterford  mica  prospect. — An  old  mica  mine  located  in  the 
southwestern  part  of  the  town  near  the  Sweden  line  was  visited  by 
the  writer  in  September,  1906.  It  consists  of  a single  pit  about  40 
feet  long,  15  feet  wide,  and  15  feet  in  depth,  located  on  an  eastern 
hillside.  The  predominant  rock  at  this  locality  is  a gray  muscovite- 
biotite  granite  varying  somewhat  in  texture  but  mostly  fine  grained. 
It  differs  in  shade  from  point  to  point,  owing  mainly  to  variations  in 
the  amount  of  biotite  it  contains. 

Under  the  microscope  the  texture  is  seen  to  be  typically  granitic 
and  nearly  equigranular.  The  rock  is  very  fresh  and  consists  in 
order  of  abundance  of  quartz,  microcline,  biotite,  plagioclase  feld- 
spar, and  muscovite.  The  plagioclase  appears  to  have  the  compo- 
sition of  oligoclase  (refractive  index  > microcline  and  > = < Canada 
balsam;  extinction  angles  low).  Much  of  the  quartz  shows  rounded 
outlines  and  is  inclosed  by  microcline.  This  quartz  appears  to  rep- 
resent the  earliest  crystallization,  even  the  biotite  plates  conform- 
ing to  its  rounded  outlines.  Microcline  and  other  quartz  are  plainly 
later  crystallizations. 

Locally  aggregations  of  biotite  in  the  granite  form  flat  lenticles, 
many  of  irregular  form  and  variously  oriented.  Biotitic  aggregations 
are  also  present  in  the  finer  portions  of  the  pegmatite. 

The  pegmatite  penetrates  the  granite  in  an  exceedingly  irregular 
manner,  locally  with  the  most  gradual  transition.  The  pegmatite 
shows  great  variation  in  coarseness,  the  coarsest  portions  containing 
crystals  of  orthoclase  1J  to  2 feet  across.  Its  mineral  constituents 
appear  to  be  identical  with  those  of  the  granite,  though  present 
perhaps  in  somewhat  different  proportions.  The  dominant  feldspar 
is  microcline  (with  some  orthoclase) ; oligoclase  is  present  in  subordi- 
nate amounts  (refractive  index  > microcline  and  about  = balsam; 
extinction  angles  up  to  12°  and  13°). 

In  texture  and  mineral  composition  the  granite  of  this  quarry  is  very 
similar  to  that  at  Rumford  Falls  (pp.  94-95).  Both  granite  masses 
are  of  relatively  small  extent  and  exhibit  within  short  distances 
differences  in  composition  more  marked  than  is  characteristic  of 
the  normal  granites  of  the  large  granite  areas  of  the  State.  In  the 
granite  of  Waterford  the  tendency  toward  segregation  is  further 
shown  by  the  presence  of  the  biotite  nodules  already  mentioned.  In 
both  localities  granite  is  so  similar  in  mineral  composition  to  the 
associated  pegmatite  and  the  gradation  from  one  rock  to  the  other  is 
in  many  places  so  gradual  and  irregular  that  ft  seems  necessary  to  con- 
clude that  granite  and  pegmatite  crystallized  fron  the  same  magmatic 
source  at  nearly  the  same  time.  Some  of  the  pegmatite  shows 
megascopic  evidence,  in  the  presence  of  thin  irregular  skins  of  musco- 
vite and  other  secondary  foliated  minerals  along  certain  planes 
through  the  rock,  of  very  slight  internal  movements  subsequent  to 


104 


PEGMATITES  AND  ASSOCIATED  ROCKS  OF  MAINE. 


its  solidification.  Microscopically  the  effects  of  these  movements 
are  recognizable  in  local  granulation  within  certain  quartz  and  feld- 
spar individuals  and  marked  strain  in  others. 

The  coarsest  portions  of  the  pegmatite  have  been  worked  for  mica. 
A few  of  the  muscovite  books  are  as  much  as  1 foot  across,  but  the 
majority  are  under  4 inches.  The  larger  plates  are  only  in  part  clear, 
being  injured  by  ruling  and  twinning.  The  writer  saw  no  plates  that 
would  cut  clear  pieces  larger  than  2 by  3 inches,  and  even  such  as 
would  were  rare.  Most  of  the  material  could  be  utilized  only  for 
scrap  mica.  The  property  hardly  appears  to  merit  further  develop- 
ment. 

Beech  Hill  mica  mine. — Another  mica  mine,  located  a few  miles 
north  of  the  first,  on  the  farm  of  George  L.  Kimball,  on  Beech  Hill, 
represents  the  most  serious  attempt  at  mica  mining  that  has  been 
made  in  the  State.  The  mica  occurs  as  a constituent  of  a sill-like 
mass  of  coarse  pegmatite,  which  dips  to  the  east  at  about  30°.  Its 
thickness  is  at  least  12  feet,  the  base  not  being  exposed.  Commer- 
cial mica  is  confined  to  a zone  about  5 feet  thick  in  the  lowest  part 
of  the  pegmatite  layer  as  now  exposed.  Within  this  5-foot  zone 
muscovite  is  estimated  to  form  from  10  to  20  per  cent  of  the  material 
of  the  pegmatite. 

Some  of  the  masses  of  pure  orthoclase  feldspar  associated  with  the 
mica  are  5 feet  across,  but  the  total  quantity  present  is  not  sufficient 
to  make  it  of  commercial  importance.  Intergrowths  of  quartz  and 
muscovite  are  common. 

The  pegmatite  contains  no  biotite  and  no  black  tourmaline.  The 
associated  rock  is  a granite  gneiss,  and  both  gneiss  and  pegmatite  are 
intruded  by  a dike  of  diabase. 

Some  of  the  muscovite  books  are  1 foot  across,  but  most  of  them 
are  under  5 inches.  The  larger  plates  are  invariably  cut  up  by 
ruling  planes  into  a number  of  smaller  pieces.  Much  of  the  mica  is 
worthless  for  anything  but  scrap  because  of  the  prevalence  of  ruling, 
wedge  structure,  and  twinning.  Most  of  the  thumb-trimmed  mate- 
rial seen  by  the  writer  was  in  pieces  2 or  3 by  3 inches  in  size.  The 
mine  was  not  being  worked  at  the  time  of  the  writer’s  visit  in  Sep- 
tember, 1906,  and  although  several  tons  of  mica  lay  in  the  trimming 
sheds,  the  best  of  the  output  was  reported  to  have  been  sold.  It 
was  therefore  impossible  to  make  a wholly  fair  estimate  of  the  aver- 
age value  of  the  mica  mined,  but  the  quality  of  the  material  is  supe- 
rior to  that  from  any  other  known  locality  in  Maine  and  appears  to 
warrant  further  development. 

The  property  was  opened  in  1900  and  was  also  worked  in  1902  by 
the  Beech  Hill  Mining  Company,  who  subsequently  sold  the  prop- 
erty to  New  York  persons.  About  a ton  of  thumb- trimmed  mica 
was  marketed  at  prices  ranging  from  8 cents  to  SI  a pound,  and 


SAGADAHOC  COUNTY. 


105 


about  10  tons  of  scrap  mica  was  sold.  The  remainder  of  the  mate- 
rial quarried  was  still  in  the  mine  buildings  at  the  time  of  the  writer’s 
visit.  The  equipment  includes  a steam  drill  and  boiler  and  a shed 
where  the  trimming  was  done. 

SAGADAHOC  COUNTY. 

GEORGETOWN. 

The  rocks  of  Georgetown  are  mostly  sedimentary  schists  and 
intruded  masses  of  pegmatite,  normal  granite,  and  flow  gneiss.  The 
only  pegmatite  deposit  now  worked  is  on  the  east  side  of  Kennebec 
River,  near  its  mouth,  where  feldspar  is  quarried  by  Golding’s  Sons 
Company,  of  Trenton,  N.  J. 

Georgetown  Center.- — The  relations  between  the  pegmatite  and  schists 
on  Bay  Point  Peninsula  (see  below)  are  repeated  in  good  exposures 
at  the  four  corners  west  of  Georgetown  Center.  Here  a mass  of  peg- 
matite 10  feet  in  maximum  width  intrudes  the  schists  irregularly, 
sending  off  into  them  an  apophysis  1 foot  in  width  at  its  base,  but 
tapering  out  within  6 feet.  This  branch  shows  the  same  irregular 
pegmatitic  texture  as  the  larger  dike  but  becomes  finer  grained  as 
it  tapers.  The  bordering  schist  contains  numerous  quartz  string- 
ers, some  of  which  are  distinctly  traceable  into  the  pegmatite  and 
near  the  latter  carry  a few  mica  plates. 

On  the  hill  east  of  the  gurnet  at  Georgetown  Center  a number  of 
prospect  pits  for  feldspar  were  opened  by  J.  S.  Berry.  Black  tour- 
maline and  biotite  are  so  abundant  in  most  of  the  pegmatite  as  to 
render  it  useless  for  pottery  purposes. 

Hincldeys  Landing. — On  the  shore,  about  one-half  mile  south  of 
Hinckleys  Landing,  a pegmatite  mass  in  the  schist  gives  off  a branch 
dike  3 to  6 inches  wide,  which  very  near  where  it  leaves  the  parent 
mass  becomes  fine  grained  and  typically  granitic  in  texture. 

Golding's  feldspar  quarry. — One  of  the  most  productive  feldspar 
quarries  in  Maine,  and  one  that  has  been  worked  intermittently  for 
over  thirty  years,  is  located  near  the  east  shore  of  Todds  Bay  near 
the  mouth  of  Kennebec  River  and  is  now  owned  and  operated  by 
Golding’s  Sons  Company,  of  Trenton,  N.  J.  It  may  be  reached  by 
a drive  of  11  miles  from  Woolwich  or  by  steamer  from  Bath  to  Bay 
Point  Landing,  which  is  only  about  1 \ miles  from  the  quarry.  The 
Bath  quadrangle  of  the  United  States  Geological  Survey  includes 
this  area.  The  property  was  visited  by  the  writer  in  July,  1906,  and 
again  in  November,  1908. 

The  excavations  cover  an  area  of  about  3 acres  and  consist  of  three 
open  pits.  The  southernmost  pit,  which  is  the  oldest  and  largest, 
had  been  abandoned  for  many  years  at  the  time  of  the  writer’s  visit 


106 


PEGMATITES  AND  ASSOCIATED  ROCKS  OF  MAINE. 


in  1906,  but  in  1908  the  quarry  waste  which  had  been  dumped  in  it 
was  being  removed  and  new  excavating  had  revealed  considerable 
amounts  of  excellent  feldspar.  It  is  significant  that  much  of  the 
waste  material  dumped  into  this  pit  in  the  early  mining  is  of  good 
commercial  grade  according  to  present  standards  and  is  being  saved. 
In  the  early  days  graphic  granite  was  mostly  discarded  and  only 
practically  pure  feldspar  utilized.  This  pit  is  now  about  100  feet  in 
depth.  The  northernmost  pit,  from  which  large  amounts  of  spar 
have  recently  been  taken,  is  200  feet  long  in  a direction  N.  25°  E., 
40  to  75  feet  wide,  and  20  to  30  feet  deep. 

In  this  quarry  the  commercially  valuable  rock  is  mainly  a coarse 
graphic  intergrowtli  of  feldspar  and  quartz,  which  is  estimated  to 
comprise  about  one-half  the  total  material  excavated,  the  other  half 
being  waste  which  is  highly  quartzose  or  contains  muscovite  or  iron- 
bearing minerals.  (See  Plate  XVIII) . • 

The  quartz  of  this  quarry  is  mostly  gray  and  semiopaque,  and  in 
many  places  has  a granular  appearance.  In  a few  places  it  is  slightly 
pinkish  in  hue.  Masses  of  pure  quartz  are  usually  small,  the  largest 
observed  by  the  writer  being  a mass  6 feet  across  in  the  northern- 
most pit.  It  is  not  utilized  commercially. 

Most  of  the  feldspar  is  orthoclase  or  microcline  with  small  amounts 
of  albite.  The  following  analysis  by  the  Pittsburg  testing  laboratory 
of  the  United  States  Geological  Survey  is  of  the  best  grade  of  buff- 
colored  feldspar: 

Analyses  of  feldspar  from  Golding's  Sons  Company  quarry. 

Silica  (Si02) 

Alumina  (A1203) . . 

Iron  oxide  (Fe203) 

Lime  (CaO) 

Magnesia  (MgO) . . . 

Potash  (KoO) 

Soda  (Na20) 

Loss  on  ignition. . . 

99.  99 


65.  23 
20.  09 
.71 
None. 
None. 
11.  60 
2.  00 
.36 


Very  few  large  masses  of  pure  feldspar  are  exposed  in  the  present 
quarry  openings,  but  it  is  said  that  in  the  past  single  blasts  have 
loosened  100  tons  of  almost  pure  material.  In  the  southern  pit  a 
number  of  masses  of  pure  feldspar  several  feet  across  were  exposed 
in  1908,  but  most  of  the  rock  here  and  practically  all  exposed  in  the 
middle  and  northern  pits  is  an  intergrowth  of  quartz  and  feldspar. 
Most  of  this  intergrowtli,  however,  is  of  excellent  quality  for  pottery 
uses,  since  injurious  minerals  such  as  muscovite  and  black  tourmaline 
are  usually  confined  to  certain  portions  of  the  mass  and  can  be  readily 
separated  from  the  rest  of  the  rock  in  mining.  Although  the  graphic 


SAGADAHOC  COUNTY. 


107 


form  of  quartz  and  feldspar  intergrowth  is  the  most  common,  very 
perfect  dendritic  penetrations  of  feldspar  by  quartz  are  also  present. 

Muscovite  is  not  present  in  sufficient  amounts  to  be  of  any  com- 
mercial importance.  All  the  larger  books  are  of  the  wedge  variety. 
Graphic  intergrowths  of  quartz  and  muscovite  are  also  found  locally, 
as  are  rounded  aggregates  made  up  almost  entirely  of  small  mus- 
covite crystals  and  similar  to  those  observed  at  the  G.  D.  Willes 
quarry  in  Topsham. 

Biotite  is  almost  entirely  absent,  but  in  its  stead  occurs  black  tour- 
maline. The  latter  'is  locally  very  abundant  in  prismatic  crystals, 
some  of  which  are  to  3 inches  in  diameter  and  a foot  or  more  in 
length.  The  tourmaline  is  not  evenly  distributed  through  the 
pegmatite  but  is  confined  almost  entirely  to  certain  irregular  zones 
which  may  be  avoided  or  discarded  in  the  quarrying  process.  It  is 
more  abundantly  associated  with  the  quartz  than  with  the  feldspar. 

Garnet  occurs  in  deep  flesh-colored  crystals,  usually  small  and 
associated  with  quartz  and  muscovite.  Some  light-green  opaque 
beryl  is  found,  one  mass  penetrating  quartz  being  14  inches  long  and 
4 inches  in  diameter. 

The  contact  of  the  pegmatite  with  other  rocks  is  not  exposed  in  any 
of  the  quarry  openings,  but  is  fairly  well  shown  a few  rods  northeast 
of  the  quarry  near  the  highest  part  of  the  same  hill,  where  the  border- 
ing rocks  are  schists  which  strike  slightly  east  of  north  and  dip  nearly 
vertical.  The  contact  nearly  parallels  the  trend  of  the  schists  and 
the  pegmatite  is  plainly  intrusive,  locally  cutting  across  the  foliation 
of  the  schists  and  sending  off  broad  apophyses  into  them.  A note- 
worthy feature  of  this  contact  is  the  complete  absence  of  any  change 
in  texture  or  coarseness  in  the  pegmatite  as  the  schist  is  approached. 
A coarse  aggregate  of  black  tourmaline  crystals,  some  of  which  are 
lj  inches  in  diameter,  occurs  within  2 feet  of  the  contact;  and  graphic 
granite  of  the  same  coarseness  as  in  the  central  parts  of  the  pegmatite 
mass  occurs  along  its  border.  The  schist  is  a quartz-biotite  rock,  in 
many  places  highly  garnetiferous  and  containing  abundant  stringers 
of  white  to  brownish  quartz,  which,  at  this  point  at  least,  have  no 
traceable  connection  with  the  associated  pegmatite  and  are  no 
larger  nor  more  numerous  near  the  contact  than  some  distance  away. 
The  schist  folia  in  many  places  show  numerous  minor  contortions. 

The  present  excavations  cover  almost  the  whole  area  of  outcrop 
of  the  pegmatite  body.  Future  work  will  probably  consist  largely 
in  deepening  the  present  pit,  but  there  is  reason  to  expect  that  the 
deposit  will  continue  of  good  quality  and  of  about  the  same  dimen- 
sions to  a considerable  depth.  A number  of  other  dikes  of  pegma- 
tite of  similar  size  and  shape  occur  in  the  vicinity  and  some  of  them 
have  been  worked  to  a slight  extent.  None  of  these,  so  far  as  seen, 
show  any  large  amounts  of  feldspar  of  commercial  grade. 


108 


PEGMATITES  AND  ASSOCIATED  ROCKS  OF  MAINE. 


The  rock  is  excavated  by  steam  drilling  and  dynamite  blasting  and 
in  the  largest  pit  is  hoisted  by  derrick  and  hoisting  engine.  It  is 
broken  up  and  sorted  by  hand  and  hauled  by  wagon  one-fourth  mile 
to  the  shore,  where  it  is  transferred  to  small  sailing  barges,  which 
convey  it  either  to  vessels  for  shipment  to  Trenton  by  water  or  up 
Kennebec  River  10  miles  to  Bath  for  shipment  by  rail.  About  fifteen 
men  are  usually  employed  in  this  quarry. 

Small  Point  feldspar  quarry. — A small  feldspar  quarry,  now  aban- 
doned and  partly  filled  with  water,  is  located  one-half  mile  east  of 
the  Golding  quarry,  near  the  head  of  Sagadahoc  Bay  and  east  of  the 
highway.  It  is  a single  pit  about  75  feet  long,  35  feet  wide,  and 
probably  30  to  40  feet  in  depth,  though  only  25  feet  of  wall  shows 
above  the  water  level.  The  rock  is  similar  in  nearly  ever  respect  to 
that  quarried  at  the  Golding  quarry,  but  the  area  of  the  deposit 
seems  to  be  very  small,  schist  occurring  within  a hundred  feet  or  so 
north,  west,  and  south  of  the  pit. 

Schist-pegmatite  contacts  on  Bay  Point  Peninsula. — The  contacts 
between  the  pegmatites  and  the  schists  are  well  exposed  at  a num- 
ber of  points  along  the  shores  of  Bay  Point  Peninsula.  A few  rods 
north  of  the  steamboat  landing  at  Bay  Point  the  pegmatite  cuts 
directly  across  the  schist  folia,  sending  off  quartz  stringers  into  the 
schist.  The  pegmatite  shows  no  noticeable  change  in  texture  or 
composition  to  a point  within  about  10  inches  of  the  contact,  but 
from  there  on  tends  to  become  finer  grained  and  less  feldspathic,  the 
rock  close  to  the  contact  being  an  aggregate  of  quartz  and  muscovite. 
Muscovite  also  occurs  in  some  of  the  quartz  stringers  near  their 
point  of  departure  from  the  main  pegmatite  mass.  The  schist  near 
the  pegmatite  is  rich  in  dark-brown  tourmaline  crystals,  some  of 
which  are  one-half  inch  long  and  one-eighth  inch  in  diameter;  they 
are  probably  the  results  of  contact  metamorphism. 

Although  the  quartz  stringers  described  above  are  traceable  into 
the  pegmatite,  in  many  other  places  the  pegmatite  cuts  distinctly 
across  both  the  folia  and  quartz  stringers  of  the  schist.  In  such 
places,  although  the  quartz  stringers  may  not  be  offshoots  of  the 
pegmatite  mass  immediately  associated  with  them,  the  absence  of 
genetic  connection  with  other  pegmatite  of  the  vicinity  is  not  proved. 
Such  a connection  is  rendered  probable  by  the  presence  of  some  feld- 
spar in  a number  of  the  larger  quartz  lenses.  Near  the  north  end  of 
Bay  Point  Peninsula  one  quartz  lens  bearing  some  feldspar  is  1J 
feet  in  greatest  width  and  3 to  4 feet  in  length. 

The  conversion  of  certain  of  the  schists  into  injection  gneisses 
through  their  penetration  by  pegmatite  and  quartz  stringers  pro- 
ceeding from  a larger  pegmatite  mass  is  well  shown  in  Plate  IV,  B, 
reproduced  from  a photograph  taken  along  the  wagon  road  near  the 
center  of  Bay  Point  Peninsula.  The  large  pegmatite  mass  shown  in 


SAGADAHOC  COUNTY. 


109 


this  picture  is  quite  quartzose,  with  masses  of  pure  quartz  4 to  5 
feet  across.  The  feldspar  is  in  small  crystals  intergrown  with  quartz 
and  mica  and  does  not  occur  in  large  crystals  comparable  to  the 
quartz  masses.  The  quartz  stringers  of  the  schist  are  traceable  in 
many  instances  with  perfect  continuity  into  the  quartz  of  the  schist, 
and  a number  of  the  quartz  stringers  contain  muscovite  crystals. 
Within  1|  feet  of  the  main  pegmatite  mass  the  schist  becomes  darker 
colored  through  the  abundant  development  in  it  of  dark-brown 
tourmaline. 

On  the  east  shore  of  Kennebec  Point,  about  half  a mile  northeast 
of  the  extreme  southern  tip,  schists  are  intruded  by  pegmatitic 
granite  similar  in  mineral  composition  to  the  coarse  pegmatite  at  the 
Golding  quarry,  its  principal  constituents  being  quartz,  potash  feld- 
spar, muscovite,  and  black  tourmaline.  The  average  size  of  grain 
in  this  granite  is  not  over  one-fourth  inch,  although  some  of  the  feld- 
spars are  3 inches  long.  None  of  the  black  tourmaline  crystals  are 
over  one-fourth  inch  and  they  average  only  about  one-eighth  inch 
in  width.  It  is  significant  that  the  minerals,  especially  the  black 
tourmaline,  show  a noticeable  amount  of  parallel  orientation  in  cer- 
tain parts  of  the  ledge,  indicating  a certain  amount  of  flowing  move- 
ment during  crystallization.  The  rock  becomes  finer  grained  within 
8 or  10  inches  of  the  schist  contact.  This  rock  gives  every  indica- 
tion of  being  intermediate  in  its  character  between  normal  granite 
and  the  typical  coarse  pegmatite  of  this  region. 

TOPSHAM. 

The  rocks  of  the  town  of  Topsham  are  qoartz-mica  schists  which 
have  been  intruded  by  pegmatite,  by  flow  gneisses  of  granitic  com- 
position, and  to  some  extent  by  granite.  Exposures  showing  the 
characters  and  relationships  of  these  rocks  are  plentiful  and  excellent. 

Distribution  of  the  quarries. — The  pegmatites  of  the  town  are  now 
worked  for  feldspar  at  several  points  and  were  once  worked  at  a 
number  of  others  now  abandoned.  The  quarries  all  lie  within  a belt 
about  a mile  in  width,  extending  from  Mount  Ararat,  near  Topsham 
village,  in  a northeasterly  direction  nearly  to  the  Topsham-Bowdoin- 
ham  line.  Within  this  belt  are  eight  quarries,  only  three  of  which 
are  now  active,  and  a number  of  prospect  pits.  It  is  significant  that 
the  line  of  distribution  of  these  quarries  corresponds  closely  with  the 
trend  of  the  metamorphosed  sedimentary  schists  into  which  the 
pegmatites  were  intruded.  Because  of  the  soil  covering  it  is  impos- 
sible to  determine  the  exact  limits  of  the  coarse  pegmatite  bodies 
exposed  at  each  of  these  eight  quarries,  but  it  is  evident  from  a study 
of  the  rocks  between  the  various  quarries  that  the  pegmatite  bodies 
which  are  worked  are  not  all  of  them  parts  of  a single  pegmatite 
mass  but  are  more  or  less  detached  intrusions  in  a region  where  the 


110 


PEGMATITES  AND  ASSOCIATED  ROCKS  OF  MAINE. 


rocks  are  mainly  schists.  Within  the  belt,  however,  the  pegmatitic 
intrusions  are  more  numerous  and  are  some  of  them  of  coarser  tex- 
ture than  in  the  surrounding  country.  If  we  may  use  the  form  of 
the  smaller  and  finer-grained  pegmatite  masses  as  an  index  to  that 
of  the  larger  and  coarser  ones  (which  are  commercially  valuable), 
the  latter  are  probably,  for  the  most  part,  somewhat  elongate  in  a 
direction  slightly  east  of  north,  parallel  to  the  general  trend  of  the 
inclosing  schists  and  gneisses. 

Products  of  the  quarries. — Feldspar  is  the  only  mineral  of  much 
commercial  importance  at  any  of  these  quarries.  Quartz  of  excel- 
lent quality  is  present  in  considerable  amounts  and  is  often  saved  in 
the  quarrying  process,  though  at  present  finding  but  slight  market. 
At  some  of  the  quarries  tourmalines  and  aquamarines  of  gem  quality 
are  now  and  then  obtained.  A description  of  the  quarries  in  the 
order  of  their  distribution  from  southwest  to  northeast  is  given  below. 

Mount  Ararat  feldspar  quarries. — A quarry  from  which  feldspar 
and  quartz  have  been  obtained  is  situated  on  the  east  slope  of  Mount 
Ararat,  about  1 mile  north  of  Topsham  village.  The  deeper  part  of 
the  excavation  is  about  40  feet  long  from  east  to  west,  10  feet  wide, 
and  12  feet  in  maximum  depth.  A shallow  excavation  adjacent  to 
the  northwest  part  of  the  deeper  pit  covers  an  area  of  about  20  by  30 
feet.  The  quarry  has  not  been  operated  for  several  years. 

The  lower  pit  exposes  considerable  amounts  of  clean,  white,  gray, 
and  nearly  black  semi  opaque  quartz  but  shows  few  masses  of  pure 
feldspar  more  than  3 or  4 inches  in  diameter.  Though  feldspar  wa's 
the  principal  mineral  sought,  the  quartz  was  saved  in  the  quarrying 
process  and  tons  of  it  are  now  piled  near  the  pit.  The  feldspar  is 
cream  colored  to  nearly  white  and  is  shown  by  microscopic  examina- 
tion to  be  principally  microcline,  with  occasional  very  small  amounts 
of  the  white  soda  feldspar,  albite.  In  the  upper  and  shallower 
portion  of  the  quarry  the  amount  of  pure  quartz  is  less  and  the  amount 
of  pure  feldspar  is  greater  than  in  the  lower  portion.  Some  of  the 
masses  of  pure  feldspar  there  are  3 to  4 feet  across.  They  grade  into 
a coarse  graphic  intergrowth  of  quartz  and  feldspar  and  the  latter 
into  extremely  fine  graphic  granite.  Only  the  pure  feldspar  and  the 
coarse  graphic  granite  were  used  commercially.  Of  the  iron-bearing 
minerals  which  would  injure  the  quality  of  the  feldspar  for  pottery 
purposes,  black  tourmaline  is  almost  entirely  absent  and  black  mica 
(biotite)  is  rare.  Garnet  is  rather  an  abundant  constituent,  but  is 
associated  mainly  with  the  muscovite  and  with  the  finer-grained 
portions  of  the  pegmatite,  and  only  rarely  with  the  more  feldspathic 
parts  that  are  commercially  available.  Magnetite  occurs  rarely  in 
small  irregular  octahedra. 

Muscovite  or  white  mica  is  also  an  abundant  constituent  of  the 
pegmatite  as  exposed  in  the  upper  pit.  It  is  pale  green  to  nearly 


SAGADAHOC  COUNTY. 


Ill 


colorless  and  occurs  in  books,  some  of  which  are  8 to  10  inches  in 
diameter.  The  great  bulk  of  the  muscovite  is  of  the  wedge  variety 
and  shows  twinning;  it  could  be  utilized  commercially  only  as  scrap 
mica.  A small  amount  is  plate  mica  and  splits  readily  into  sheets, 
which  when  trimmed  may  measure  4 by  5 inches,  though  mostly 
smaller.  Most  of  this  plate  mica  incloses  between  its  lamellse  thin 
branching  crystals  of  magnetite.  A few  small  masses  of  columbite, 
generally  exhibiting  very  imperfect  crystal  forms,  are  found  in  the 
quartz-feldspar  masses. 

The  wall  rock  of  schist  or  gneiss  is  nowhere  exposed  at  this  quarry, 
and  the  soil  covering  makes  it  impossible  to  trace  the  exact  limits  of 
the  deposit.  If  one  may  judge  from  neighboring  masses  of  pegma- 
tite whose  boundaries  are  exposed,  this  mass  is  probably  more  or  less 
irregular  in  outline  and  somewhat  elongate  in  a direction  parallel  to 
the  trend  of  the  neighboring  schists — that  is,  somewhat  east  of  north. 
The  deposit  does  not  appear  to  be  very  extensive,  but  the  quality  is 
good,  and  there  seems  to  be  warrant  for  further  development  work  on 
a small  scale. 

A second  small  feldspar  quarry,  on  the  northern  slope  of  Mount 
Ararat,  consists  of  a single  hillside  pit  about  150  feet  long,  30  feet 
in  average  width,  and  20  feet  in  greatest  depth.  It  was  last  worked 
in  1 905.  The  rock  is  a wholly  irregular  association  of  quartz,  feldspar, 
muscovite,  biotite,  and  garnet,  with  smaller  amounts  of  rarer  minerals. 
The  quartz  is  prevailingly  dark  gray  in  color  and  semiopaque,  but  in 
some  places  is  white  and  in  a few  nearly  black.  A number  of  the 
pure  quartz  masses  are  3 to  4 feet  across;  one,  flat  lying  and  exposed 
at  the  base  of  one  of  the  quarry  walls,  is  5 feet  in  maximum  width 
and  25  feet  in  length,  with  very  irregular  boundaries. 

Most  of  the  feldspar  is  pale  pink  in  color,  but  certain  portions  are 
cream  colored,  and  others  decidedly  red.  Microscopic  examination 
shows  that  the  feldspar  belongs  mainly  to  the  potash  varieties  ortlio- 
clase  and  microcline,  the  former  greatly  predominating.  With  these 
are  associated  small  amounts  of  the  soda  feldspar,  albite,  which  is  fre- 
quently intergrown  microscopically  with  the  orthoclase  or  microcline. 
Throughout  most  of  the  quarry  the  masses  of  pure  feldspar  are  not 
over  4 to  5 inches  across,  though  a few  crystals  measure  2 to  3 feet. 
The  bulk  of  the  material  quarried  for  pottery  use  is  a graphic  inter- 
growth of  feldspar  and  quartz,  most  of  it  coarser  than  that  found  at 
the  quarry  on  the  eastern  slope  of  Mount  Ararat.  The  quartz  thus 
intergrown  with  the  feldspar  commonly  assumes  branching  or  den- 
dritic forms,  a characteristic  not  observed  in  most  of  the  pegmatite 
deposits. 

Muscovite  of  the  wedge  variety  occurs  sparingly  in  books  up  to  6 
inches  in  greatest  diameter.  No  clear  plate  mica  was  observed. 
Of  very  common  occurrence  are  graphic  intergrowths  of  muscovite 


112 


PEGMATITES  AND  ASSOCIATED  EOCKS  OF  MAINE. 


and  quartz,  many  single  crystals  of  muscovite  with  roughly  hexag- 
onal outline  grading  outward  into  a fringe  of  graphically  intergrown 
muscovite  and  quartz.  In  some  places  muscovite  and  feldspar  are 
graphically  intergrown.  The  quartz  of  these  muscovite  intergrowths 
is  in  many  places  continuous  with  quartz  intergrown  with  feldspar. 

Biotite  is  much  more  abundant  than  at  the  quarry  on  the  eastern 
side  of  Mount  Ararat  and  dominates  over  muscovite.  It  occurs  in 
the  characteristic  lath-shaped  crystals,  many  of  which  have  a length 
of  2 feet,  a width  of  4 to  5 inches,  and  a thickness  of  one-half  inch  to 
1 inch.  The  largest  biotite  crystal  observed  was  feet  long,  2\ 
feet  wide,  and  1 to  2 inches  thick.  These  crystals  penetrate  the  peg- 
matite mass  in  every  conceivable  direction. 

Garnet  is  rather  abundant  and  is  generally  dark  red  and  submetal- 
lic  in  appearance.  In  some  places  it  is  intergrown  with  quartz  and 
in  others  with  both  quartz  and  muscovite.  One  garnet  crystal  was 
2 \ inches  across.  It  is  most  abundant  in  the  finer  grained  portion 
of  the  pegmatite  and  in  those  portions  rich  in  muscovite  and  is  rare 
in  the  parts  which  are  used  commercially.  Magnetite  occurs  only 
rarely  in  imperfect  octahedra  showing  step  structure. 

Schists  and  gneisses  are  nowhere  exposed  in  this  quarry  and  near-by 
outcrops  are  not  numerous,  so  that  it  is  impossible  to  determine  the 
form  or  area  of  the  pegmatite.  On  the  north  wall  of  the  quarry  a 
small  mass  of  fine-grained  granite  showing  locally  a somewhat 
gneissic  structure  is  exposed  and  is  intruded  by  the  pegmatite,  the 
latter  cutting  across  the  banding  of  the  granite  gneiss,  though  there 
is  crystallographic  continuity  between  the  two. 

The  amount  of  feldspar  of  commercial  quality  now  exposed  is  not 
large,  and  the  abundance  of  biotite  and  garnet  render  much  of  the 
material  valueless  for  pottery  uses.  The  extent  of  the  deposit  can 
not  be  accurately  predicted,  but  is  probably  not  very  great.  Further 
development  on  a small  scale  could  probably  be  profitably  under- 
taken and  might  reveal  some  good  spar  not  now  exposed.  The 
deposit  is  located  2 miles  from  the  Maine  Central  Railroad  station 
at  Topsham.  The  nearest  point  on  the  railroad  is  only  three-fourths 
of  a mile  southeast  of  this  quarry  and  the  one  previously  described, 
but  there  is  no  wagon  road  available  in  this  direction. 

Fisher’s  feldspar  quarry.— A.  small  quarry  not  now  worked  is  situ- 
ated miles  west-northwest  of  Cathance  station  along  the  northern 
valley  slope  of  Cathance  River.  This  quarry,  which  was  formerly 
operated  for  feldspar  by  J.  A.  Fisher,  consists  of  a single  pit  about 
150  feet  long  from  north  to  south,  20  feet  or  so  in  average  width, 
and  about  18  feet  in  maximum  depth.  It  is  located  on  a southern 
hill  slope. 

As  in  most  of  the  other  feldspar  quarries,  there  is  no  regularity 
in  the  arrangement  of  the  constituent  minerals  with  the  single 


SAGADAHOC  COUNTY. 


113 


exception  of  muscovite,  which  occurs  principally  along  certain  zones 
which  have,  however,  no  definite  trend  with  respect  to  the  general 
outlines  of  the  deposit. 

The  quartz  is  white  to  gray  in  color,  but  no  very  large  masses  are 
exposed. 

The  feldspar  is  cream  colored  and  is  shown  by  microscopic  exami- 
nation to  be  mainly  microcline  with  some  orthoclase.  Small  amounts 
of  the  soda  feldspar,  albite,  probably  occur  as  in  the  other  quarries 
in  this  vicinity,  though  none  was  observed  by  the  writer.  One  mass 
of  pure  feldspar,  3 to  4 feet  wide  and  10  feet  high,  exposed  on  the 
west  wall  of  the  quarry,  passes  by  perfect  gradations  into  a coarse 
graphic  intergrowth  with  quartz  and  this  in  turn  into  a much  finer 
graphic  intergrowth.  As  in  most  of  the  feldspar  quarries,  the  coarse 
graphic  granite  forms  the  bulk  of  the  material  mined  for  pottery 
purposes.  The  chemical  composition  of  graphic  granites  from  this 
quarry  is  discussed  on  pages  40,  124,  and  their  appearance  is  shown  in 
Plate  XVIII. 

The  muscovite,  so  far  as  present  exposures  show,  is  all  of  the  wedge 
variety  and  is  mainly  confined  to  certain  zones  which  penetrate  the 
pegmatite  irregularly  (see  PI.  IX,  A,  and  p.  26);  being  localized  in 
this  manner,  it  does  not  seriously  interfere  with  the  feldspar  mining. 
The  muscovite  books  are  nearly  all  characterized  by  twinning  and 
wedge  structure.  No  plate  mica  was  observed.  Graphic  inter- 
growths of  quartz  and  muscovite  are  common.  In  some  parts  of 
the  pegmatite  biotite  dominates  over  muscovite ; it  is  usually  most 
abundant  in  the  finer-grained  portions. 

An  examination  by  Wright  and  Larsen  of  the  white  quartz  of  the 
larger  quartz  areas  at  this  quarry  showed  that  it  probably  crystal- 
lized under  low-temperature  conditions.  Quartz  from  the  coarser 
phases  of  the  graphic  granite  was  also  examined  and  though  the 
results  were  not  conclusive  they  indicated  that  the  quartz  may  have 
crystallized  under  high-temperature  conditions.  Since  the  areas  of 
pure  quartz  are  closely  adjacent  to  those  of  graphic  granite  and 
indeed  grade  into  them  most  irregularly,  these  results  suggest  that 
the  crystallization  temperatures  of  the  pegmatite  mass  as  a whole 
were  not  far  from  the  inversion  point  of  quartz  (about  575°  C.); 
however,  the  imperfect  character  of  the  data  must  be  borne  in  mind. 
This  matter  is  discussed  in  more  detail  on  pages  36-39. 

Dutcrops  are  not  numerous  enough  in  the  immediate  vicinity  to 
determine  the  extent  or  form  of  the  pegmatite  body.  The  materials 
exposed  in  the  present  excavation  seem  to  indicate  that  a consid- 
erable supply  of  spar  is  still  available  and  seem  to  warrant  further 
development. 

William  Willes  feldspar  quarry. — A small  quarry  situated  \\  miles 
northwest  of  Cathance  station  and  operated  by  William  Willes  for  the 
63096°— Bull.  445—11 8 


114 


PEGMATITES  AND  ASSOCIATED  ROCKS  OF  MAINE. 


Trenton  Flint  and  Spar  Company  was  opened  early  in  1906.  It 
occupies  an  area  of  a little  more  than  1 acre,  and  its  average  depth  is 
about  10  feet.  Natural  drainage  is  possible  at  present  depth,  but 
further  excavation  will  necessitate  pumping.  The  rock  is  a wholly 
irregular  association  of  quartz,  feldspar,  mica,  and  rarer  minerals. 

The  quartz  is  mainly  light  gray  in  color  and  occurs  locally  in  pure 
masses  5 or  6 feet  in  diameter.  Many  even  of  the  larger  quartz 
masses  exhibit  crystal  faces  along  their  contact  with  other  minerals. 
Quartz  is  saved  in  the  quarrying  process  but  finds  only  a very  irreg- 
ular market. 

The  feldspar  is  buff  colored  and  is  shown  by  microscopic  examina- 
tion to  be  mainly  ortlioclase  and  microcline.  The  soda  variety, 
albite,  also  occurs  but  forms  only  a small  percentage  of  the  total  mass 
of  feldspar;  a few  crystals  of  albite  are  4 to  5 inches  across.  As  at 
most  of  the  Maine  feldspar  quarries,  the  great  bulk  of  the  material 
quarried  for  pottery  purposes  is  a coarse  graphic  intergrowth  of  quartz 
with  potash  feldspar.  In  the  northern  part  of  the  quarry  a mass  of 
pure  feldspar  10  feet  across  is  exposed  on  a glaciated  surface. 

Muscovite  occurs  in  grapihc  intergrowth  with  quartz  and  also  in 
books,  the  latter  being  mostly  wedge  mica.  Some  of  these  books 
are  10  inches  across.  The  total  amount  of  muscovite  present  is  not 
sufficient  to  make  it  worth  while  to  save  it  in  quarrying. 

Biotite  is  about  equally  as  abundant  as  muscovite  and  occurs  in 
characteristic  lath-shaped  crystals;  one  of  these  was  4 feet  long,  8 
inches  wide,  and  1 inch  thick.  Much  of  the  biotite  is  decomposed  to 
what  appears  to  be  chlorite  colored  with  hematite. 

Garnet  is  moderately  abundant,  usually  occurring  in  compound 
crystals  of  dark-red  color  with  submetallic  luster. 

Beryl  is  moderately  abundant,  some  hexagonal  crystals  being  10 
inches  in  diameter.  Some  of  the  smaller  crystals  are  partly  trans- 
parent and  have  been  sold  to  mineral  collectors. 

Some  columbite  is  found  in  small  imperfectly  developed  crystals 
but  is  not  sufficiently  abundant  to  be  of  commercial  consequence. 

In  one  place  in  the  quarry  a small  amount  of  hornblendic  granite 
gneiss  occurs.  The  pegmatite  cuts  across  the  foliation  of  the  granite 
gneiss  and  is  plainly  somewhat  the  younger.  Its  exact  attitude  and 
boundaries  could  not  be  determined  because  of  the  scarcity  of  out- 
crops in  the  vicinity,  but  it  is  probable  that  further  stripping  near  the 
present  workings  will  reveal  considerable  amounts  of  commercially 
valuable  spar. 

At  the  time  of  the  writer’s  visit  seven  laborers  were  employed  in  the 
quarry  besides  the  foreman  and  the  superintendent.  The  rock  is 
hauled  by  two  2-horse  teams  a distance  of  1J  miles  to  the  feldspar 
mill  near  Cathance  station. 


SAGADAHOC  COUNTY. 


115 


Maine  Feldspar  Company's  quarry. — A small  feldspar  quarry  a few 
rods  southeast  of  the  one  just  described  was  opened  in  1906  by  the 
Maine  Feldspar  Company,  of  Auburn,  Me.  The  rock,  which  is  similar 
in  every  way  to  that  at  the  William  Willes  quarry,  is  hauled  by  team 
about  li  miles  to  Cathance  station  and  from  there  shipped  by  rail  to 
the  Maine  Feldspar  Company’s  mill  at  Littlefield,  3 miles  southwest 
of  Auburn. 

G.  D.  Willes  feldspar  quarry. — A feldspar  quarry  operated  for  the 
Trenton  Flint  and  Spar  Company  by  G.  D.  Willes,  of  Brunswick,  is 
situated  about  2 miles  northwest  of  Cathance  station  and  is  the 
oldest  and  by  far  the  largest  of  the  Topsham  quarries.  Its  irregular 
opening  covers  several  acres  and  the  material  is  excavated  from 
several  levels,  the  greatest  depth  being  about  50  feet. 

Although  the  great  bulk  of  the  commercial  spar  now  taken  from  this 
quarry  is  a coarse  graphic  intergrowth  of  feldspar  and  quartz,  masses 
of  pure  quartz  and  of  pure  feldspar  occur  which  are  larger  than  those 
seen  at  any  other  quarry  in  the  State.  A single  mass  of  pure  white 
quartz  in  the  northern  part  of  the  quarry  is  50  feet  long  and  is  exposed 
for  a height  of  10  feet.  The  pegmatite  is  in  general  coarser  at  the 
northern  than  at  the  southern  end  of  the  quarry. 

The  feldspar  also  occurs  here  and  there  in  crystals  of  large  size,  one 
in  the  northern  part  of  the  quarry  measuring  15  feet  across.  The 
bulk  of  the  feldspar,  as  shown  by  microscopic  study,  belongs  to  the 
potash  varieties  orthoclase  and  microcline,  but  some  small  masses, 
not  many  of  them  more  than  a few  inches  across,  are  of  the  white  soda 
feldspar,  albite. 

On  the  wall  at  the  extreme  southern  encf  of  the  quarry  certain  por- 
tions of  the  pegmatite  up  to  a foot  or  so  in  width  are  a micrographic 
granite  and  exhibit  the  peculiar  structure  described  on  page  123. 

Muscovite  is  concentrated  along  certain  belts  traversing  the  peg- 
matite mass  in  various  directions.  Their  general  form  is  similar  to 
that  shown  in  Plate  IX,  A.  The  central  portions  for  a width  of  a few 
inches  consist  of  an  aggregate  of  heterogeneously  disposed  muscovite 
plates,  few  of  them  over  one-fourth  inch  in  diameter.  From  this  finer- 
grained  portion  spearhead-shaped  books  of  muscovite,  some  of  them 
a foot  in  length,  showing  wedge  structure,  project  in  a direction  nearly 
at  right  angles  to  the  general  plane  of  the  mica  belt.  In  the  southern 
part  of  the  quarry  muscovite  occurs  also  in  nearly  equidimensional 
aggregates,  in  some  places  5 feet  across,  made  up  of  small,  hetero- 
geneously arranged  plates  averaging  about  one-fourth  inch  across. 
From  their  borders  these  muscovite  aggregates  send  off  spearhead- 
shaped books  of  muscovite  into  the  surrounding  quartz,  feldspar, 
and  graphic  granite.  Some  graphic  intergrowths  of  quartz  and  mus- 
covite occur,  but  they  are  not  abundant.  Under  present  conditions 


116  PEGMATITES  AND  ASSOCIATED  ROCKS  OF  MAINE. 

it  would  probably  not  pay  to  save  as  scrap  mica  the  muscovite, 
obtained  in  the  feldspar  mining.  No  plate  mica  was  observed. 

Biotite  is  moderately  abundant  in  certain  parts  of  the  pegmatite. 
It  penetrates  the  feldspar  and  quartz  in  lath-shaped  masses,  the 
largest  of  which  was  2 yards  long  by  3 inches  wide  and  one-fourth 
inch  thick. 

As  in  most  other  feldspar  quarries,  small  garnets  are  abundant 
only  in  certain  portions  of  the  deposit,  the  coarser  graphic  granite 
and  the  pure  feldspar  being  almost  entirely  free  from  them,  and  they 
are  not  seriously  injurious  to  the  commercial  value  of  the  deposit. 

Cavities  up  to  1 foot  in  diameter  and  of  various  form  are  rather  a 
constant  feature  of  the  coarser  portions  of  the  pegmatite  in  the  north- 
ern part  of  the  quarry.  They  may  occur  within  the  areas  of  pure 
quartz  or  feldspar,  on  the  border  between  quartz  and  feldspar  masses, 
or  more  rarely  in  the  coarse  graphic  granite.  Usually  they  contain 
groups  of  somewhat  smoky  semitransparent  quartz  crystals,  some  of 
which  make  handsome  cabinet  specimens.  In  a few,  transparent 
green  tourmalines  and  aquamarines  (beryl)  of  gem  quality  have  been 
found. 

The  schists  and  gneisses  which  border  the  pegmatite  are  exposed  at 
the  southern  end  of  the  quarry,  where  they  show  evidence  of  much 
softening  as  a result  of  the  pegmatite  intrusion.  In  general  they  are 
rather  flat  lying.  Probably  the  pegmatite  mass  is  also  in  general 
somewhat  flat  lying,  though  very  irregular.  It  is  probable  that  the 
workable  pegmatite  does  not  extend  southward  much  beyond  the 
limits  of  the  present  pit,  but  northward  it  is  known  to  extend  into 
property  said  to  be  controlled  by  the  Maine  Feldspar  Company. 
Here  it  has  been  worked  in  the  past  from  a number  of  small  openings 
and  very  considerable  amounts  of  commercial  spar  are  still  available. 

The  methods  of  operation  at  this  quarry  are  somewhat  antiquated 
for  a working  of  this  size,  the  drilling  all  being  done  by  hand  and  the 
blasting  by  black  powder.  A tramway  carries  the  waste  to  dump 
piles  and  the  good  rock  to  stock  sheds,  from  which  it  is  loaded  into 
wagons  and  hauled  1 J miles  to  the  mill  near  Cathance  station  (p.  18). 

North  Topsham feldspar  quarry. — A feldspar  quarry  in  the  northern 
part  of  the  town  of  Topsham,  one-half  mile  west  of  Cathance  River 
and  1 mile  south  of  the  Topsham-Bowdoinham  line,  was  formerly 
operated  by  the  Trenton  Flint  and  Spar  Company,  the  rock  being 
hauled  by  team  2 miles  to  the  mill  near  Cathance  station.  The 
quarry  is  located  on  the  western  valley  slope  of  the  river  and  is  an 
irregular  opening  extending  north  and  south  along  the  hill  slope  for 
about  200  feet  and  extending  into  the  hill  for  about  40  feet.  There 
is  a complete  absence  of  any  regularity  in  the  arrangements  of  the 
pegmatite  constituents. 


SAGADAHOC  COUNTY.  117 

The  quartz  is  prevailingly  white  or  light  gray,  though  smoky  in 
some  places. 

The  feldspar  is  white  to  cream  colored,  and  is  shown  by  microscopic 
examination  to  be  mainly  orthoclase,  with  small  amounts  of  albite 
and  microcline.  The  albite  in  many  places  forms  a fine  microscopic 
intergrowth  (microperthite)  with  the  orthoclase.  Some  pure  feldspar 
masses  measure  4 to  5 feet  in  diameter,  but  the  bulk  of  the  material 
quarried  for  pottery  purposes  was  a graphic  intergrowth  of  quartz  and 
feldspar. 

Muscovite,  mostly  pale  green  in  color,  is  generally  graphically 
intergrown  with  quartz,  though  a few  books  of  clean  mica  up  to  5 or 
6 inches  in  diameter  occur.  These  are  all,  so  far  as  observed,  of  the 
wedge  variety,  and  the  quantity  is  so  small  that  it  would  be  hardly 
worth  while  to  save  them  for  scrap  mica. 

Biotite  is  not  very  abundant  in  any  part  of  the  quarry  and  in  some 
parts  is  wholly  absent.  Where  it  occurs  it  forms  thin  lath-shaped 
crystals  averaging  about  6 inches  long,  1 inch  wide,  and  one-fourth 
inch  thick. 

Garnet  is  absent  from  much  of  the  pegmatite  but  locally  is  abun- 
dant in  the  finer-grained  portions  in  crystals  from  one-sixteenth  to 
one-fourth  inch  in  diameter.  Very  rarely  a crystal  measuring  3 
inches  is  found,  and  in  these  the  garnet  is  usually  graphically  inter- 
grown with  quartz.  The  color  ranges  from  pink  to  deep  red,  with  sub- 
metallic  luster. 

The  area  and  form  of  this  pegmatite  body  could  not  be  determined 
because  of  the  scarcity  of  outcrops  in  the  vicinity  of  the  quarry,  but 
the  occurrence  at  short  distances  east  and  west  of  small  masses  of 
pegmatite  of  commercial  grade  seems  to  indicate  that  the  deposit 
may  extend  considerably  beyond  the  area  now  exposed. 

The  quantity  of  material  in  sight  and  the  freedom  of  most  of  the 
material  from  iron-bearing  minerals  favors  further  development. 

Mill  of  the  Trenton  Flint  and  Spar  Company. — The  feldspar  mill  of 
the  Trenton  Flint  and  Spar  Company  is  located  on  Cathance  Fiver 
about  one-half  mile  north  of  Cathance  station.  During  high  water 
it  utilizes  the  water  power  of  this  small  river,  but  it  is  also  provided 
with  steam  power.  Its  equipment  consists  of  three  chaser  mills  and 
four  ball  mills  of  the  usual  types.  The  grinding  process  is  that 
described  on  page  127.  The  capacity  of  the  mill  is  about  16  tons  in 
twenty-four  hours,  the  ground  spar  being  hauled  by  wagons  for  one- 
half  mile  from  the  mill  to  Cathance  station,  on  the  Maine  Central 
Railroad,  where  it  is  loaded  for  shipment. 

Vicinity  of  Topsham  village. — At  a small  road-metal  quarry  on  the 
west  slope  of  Mount  Ararat  the  dominant  rock  type  is  a hornblende 
granite  schist  of  regular  and  well-marked  foliation.  It  strikes,  in  the 


118 


PEGMATITES  AND  ASSOCIATED  DOCKS  OF  MAINE. 


main,  about  N.  35°  E.  and  dips  50°  SE.  In  both  megascopic  and 
microscopic  appearance  it  is  practically  identical  with  the  lighter 
phases  of  the  schist  from  the  road-metal  quarry  in  Brunswick  vil- 
lage (p.  61).  As  at  that  quarry,  dominant  acidic  bands  of  schist, 
prevailingly  pink  or  gray  in  tone,  alternate  with  smaller  amounts  of 
dark-gray  bands  of  quartz  diorite  and  other  nearly  black  bands  of 
diorite  schist.  Under  the  microscope  these  schists  show  no  cataclastic 
structures;  they  owe  their  foliated  structure  to  parallel  elongation  of 
the  hornblende  grains  and  to  some  extent  also  of  the  grains  of  biotite 
and  quartz.  Nothing  either  in  their  texture  or  their  composition 
indicates  that  they  are  not  primary-flow  gneisses. 

Both  in  the  lighter  and  darker  phases  of  the  schist,  but  much  more 
abundantly  in  the  lighter,  are  coarser  bands  of  pegmatitic  texture, 
consisting  mainly  of  quartz  and  feldspar,  with  some  biotite  and  mag- 
netite. Many  of  these  are  parallel  to  the  foliation  of  the  schist  and 
are  of  even  width  and  uniform  character  for  several  yards.  Others, 
especially  the  larger  masses,  cut  distinctly  across  the  schist  folia,  the 
contact  being  sharp  and  without  suggestion  of  absorption. 

An  interesting  feature  of  some  of  the  pegmatite  bands  which  par- 
allel the  foliation  of  the  schists  is  the  presence  in  them  of  a slight  foli- 
ation parallel  to  that  of  the  inclosing  schist.  As  in  the  schist,  this 
foliation  is  defined  by  bands  richer  than  the  bordering  portions  in 
hornblende  and  biotite.  In  one  place  a faint  foliation  is  perceptible 
in  the  center  of  a pegmatite  mass  1J  feet  wide  that  cuts  across  the 
foliation  of  the  schists.  It  does  not  parallel  the  trend  of  the  dike 
but  does  parallel  the  foliation  of  the  inclosing  schist  and  is  defined 
by  the  arrangement  of  the  quartz  in  elongate  and  somewhat  irregu- 
lar bands.  As  there  is  no  evidence  of  appreciable  absorption  of  the 
schist  by  the  pegmatite  magma,  and  also  no  evidence  of  metamor- 
phism subsequent  to  the  intrusion  of  the  pegmatite,  such  foliation  in 
the  pegmatite  is  strongly  suggestive  of  parallel  flowing  movements 
in  the  schist  and  in  some  of  the  pegmatite.  The  field  and  microscopic 
evidence  on  the  whole  favors  the  conception  that  the  schists  are  of 
primary  or  flow-igneous  origin,  and  that  some  of  the  pegmatite  was 
crystallizing  before  flowage  had  entirely  ceased  in  the  bordering 
schist,  but  that  other  portions  of  the  pegmatite  were  intruded  after 
the  schist  had  completely  solidified.  The  practical  identity  in  min- 
eral character  between  the  different  masses  of  pegmatite  at  this  quarry 
suggests  that  the  distinctly  intrusive  portions  were  only  slightly  later 
crystallizations  than  their  host  and  that  all  the  pegmatite  had  the 
same  magmatic  source. 

One  of  the  largest  masses  of  graphic  granite  observed  was  on  the 
west  slope  of  the  180-foot  hill  in  the  sharp  bend  of  Androscoggin 
Biver  just  west  of  Brunswick.  The  ledge,  which  is  in  plain  sight 
from  the  railroad  track,  is  150  feet  long  and  averages  25  feet  wide. 


FELDSPAR. 


119 


Practically  this  whole  mass  is  a graphic  intergrowth  of  quartz,  with 
white  to  pale  pink  orthoclase  and  microcline.  Some  of  the  feldspar 
crystals  of  tliis  intergrowth  are  shown  by  reflections  from  their  cleav- 
age faces  to  be  feet  across.  The  coarseness  varies  rapidly  from 
point  to  point  even  within  the  range  of  a single  feldspar  individual. 
At  the  south  end  of  the  outcrop  the  graphic  granite  grades  into  peg- 
matite of  irregular  texture,  showing  some  masses  of  pure  feldspar 
2 to  3 inches  across.  Both  the  graphic  granite  and  this  irregular- 
textured  pegmatite  inclose  scattered  biotite  laths. 

At  the  south  end  of  this  exposure  also  there  is  some  associated 
gray  gneiss.  In  one  place  the  pegmatite  cuts  directly  across  the 
folia  of  the  gneiss.  In  other  places  graphic  granite  forms  knots  or 
short  lenses  up  to  6 inches  in  width  between  the  gneiss  folia.  The 
mass  of  graphic  granite  exposed  in  tliis  ledge  is  the  largest  contin- 
uous mass  observed  by  the  writer  in  the  State. 

ECONOMICALLY  IMPORTANT  PEGMATITE  MINERALS. 

FELDSPAR. 

The  feldspars  are  compounds  of  alumina  and  silica  with  one  or 
more  of  the  bases  potash,  soda,  and  lime;  rarely  barium  is  present. 
They  fall  into  two  principal  groups,  the  potash-soda  feldspars  and 
the  lime-soda  feldspars,  both  of  which  may  be  present  in  the  same 
deposit  or  even  intergrown  in  the  same  crystal. 

POTASH-SODA  FELDSPARS. 

The  principal  representatives  of  the  potash-soda  feldspar  group 
are  orthoclase  and  microcline,  both  of  which  have  the  composition 
KAlSigOg  or  K20.Al203.6Si02.  These  two  varieties  have  also  the 
same  crystal  form  and  are  similar  in  most  of  their  physical  proper- 
ties. For  commercial  purposes  they  may  be  regarded  as  identical, 
for  they  can  not  be  distinguished  from  each  other  with  the  unaided 
eye  and  are  often  associated  in  the  same  crystal.  The  theoretical 
percentage  composition  of  pure  orthoclase  or  microcline  is  silica 
(Si02),  64.7  per  cent;  alumina  (A1303),  18.4  per  cent;  and  potash 
(K20),  16.9  per  cent.  Soda  may  partly  or  completely  replace  potash 
in  these  feldspars.  If  it  is  more  abundant  than  the  potash,  the  feld- 
spar is  called  anorthoclase. 

The  feldspar  of  the  potash-soda  group  mined  in  the  United  States 
is  mostly  pale  flesh  colored  to  nearly  white,  though  that  from  Bed- 
ford, N.  Y.,  is  reddish  and  that  from  near  Batchellerville,  N.  Y.,  is 
pearl  gray.  The  potash  spars  from  Norway  and  from  Bedford, 
Ontario,  are  reddish  in  color.  The  cause  of  the  reddish  color  is  not 
definitely  known,  but  in  some  feldspars  it  seems  to  be  due  to  the 
presence  of  small  quantities  of  finely  divided  iron  oxide.  The  per- 


120  PEGMATITES  AND  ASSOCIATED  ROCKS  OF  MAINE. 

centage  of  iron  oxide  is  smaller,  however,  in  many  pink  feldspars 
than  in  those  of  lighter  color.  All  the  pink  spars  burn  perfectly 
white,  and  the  iron  content  is  too  small  to  be  in  the  least  detrimental 
in  pottery  manufacture.  Fresh  feldspar  is  so  hard  that  only  with 
difficulty  can  it  be  scratched  with  a knife  blade. 

As  found  in  the  quarries,  the  potash-soda  feldspars  seldom  show 
true  crystal  faces,  but  when  undecomposed  break  readily  into  angu- 
lar pieces,  bounded  in  part  by  smooth  cleavage  faces.  There  are 
three  directions  of  cleavage,  intersecting  at  definite  angles,  which 
are  practically  identical  in  orthoclase  and  microcline  and  are  only 
slightly  different  in  the  soda-bearing  feldspars  of  this  group.  Only 
two  of  the  cleavages  are  well  defined,  and  these  invariably  intersect 
approximately  at  right  angles.  Both  of  these  principal  cleavage 
surfaces  show  a high  luster,  comparable  to  that  exhibited  by  a plate 
of  glass,  though  one  cleavage  face  is  a trifle  less  brilliant  than  the 
other.  The  hardness  and  the  two  lustrous  cleavage  planes  inter- 
secting at  right  angles  are  usually  sufficient  to  identify  a mineral  as 
belonging  to  the  group  of  potash-soda  feldspars. 

Recent  experiments  have  shown  that  the  potash-rich  feldspars 
have  no  definite  melting  point,  as  metals  have,  for  example.  Fusion 
tests  made  on  finely  powdered  microcline  in  the  geophysical  labo- 
ratory of  the  Carnegie  Institution  a showed  that  at  1,000°  C.  traces 
of  sintering  were  evident;  at  1,075°  the  powder  had  formed  a solid 
cake;  at  1,150°  this  cake  had  softened  somewhat;  and  at  1,300° 
it  had  become  a viscous  liquid  which  could  be  drawn  out  into 
glassy  threads.  In  most  of  the  determinations  complete  fusion  has 
taken  place  in  the  dry  state  at  temperatures  below  Seger  cone  No.  9, 
which  fuses  at  1,310°  C.,  or  2,390°  F. 

The  great  bulk  of  the  feldspar  quarried  in  the  eastern  United  States 
and  in  Canada  belongs  to  the  class  described  above,  being  orthoclase 
or  microcline  or  an  intergrowth  of  the  two.  In  most  quarries  this  is 
associated  with  minor  quantities  of  soda  feldspar — albite  or  oligoclase — 
occurring  either  in  separate  crystals  or  delicately  intergrown  with 
the  potash  feldspar,  as  shown  in  Plate  XVII.  The  presence  of  the 
soda  spar  renders  the  ground  product  slightly  more  fusible.  The 
specific  gravity  of  orthoclase  and  microcline  varies  from  2.54  to  2.56. 

LIME-SODA  FELDSPARS  OR  PLAGIOCLASES. 

The  lime-soda  group  of  feldspars,  the  plagioclases,  as  they  are 
called,  form  a continuous  series  ranging  from  pure  soda  feldspar, 
albite,  at  one  end  to  pure  lime  feldspar,  anorthite,  at  the  other  end. 
The  chemical  composition  of  albite  is  represented  by  the  formula 
NaAlSi308  (designated  Ab)  or  Na20.Al203.6Si02,  being  similar  to  that 


a Day,  A.  L.,  and  Allen,  E.  T.,  The  isomorphism  and  thermal  properties  of  the  feldspars:  Pub.  31  Car- 
negie Inst,  of  Washington,  1905,  pp.  13-75;  also  Am.  Jour.  Sci.,  4th  ser.,  vol.  19,  1905,  pp.  93-142. 


U.  S.  GEOLOGICAL  SURVEY 


BULLETIN  445  PLATE  XVII 


MICROPHOTOGRAPH  OF  THIN  SECTION  OF  FELDSPAR  FROM  QUARRY  OF  GOLDING’S  SONS 
COMPANY,  GEORGETOWN,  MAINE.  MAGNIFIED  ABOUT  40  DIAMETERS. 

Showing  perthitic  intergrowth  of  potash  and  soda  feldspar  characteristic  of  many  commercial  feldspars. 
The  lighter  portions  with  striae  crossing  at  right  angles  are  potash  feldspar  (microcline).  The  darker 
portions  with  striations  in  only  one  direction  are  soda  feldspar  (albite). 


FELDSPAR. 


121 


of  orthoclase,  except  that  soda  is  present  in  place  of  potash.  The 
composition  of  anorthite  is  represented  by  the  formula  CaAl2Si208 
(designated  An)  or  Ca0.Al203.2Si02.  The  intermediate  members  of 
this  feldspar  series  are  mixtures  in  varying  proportions  of  the  two 
molecules  Ab  and  An  and  have  been  divided  arbitrarily,  as  shown  in 
the  following  table: 

Lime-soda  series  of  feldspars. 


Albite Ab  Ano  Ab  Ani 

Oligoclase Ab6Ani  to  AbgAii! 

Andesine AbgArii  to  AbAni 


Labradorite Ab  Ani  to  Ab  An3 

Bytownite . AbAn3  to  AbAne 

Anorthite Ab  An6  to  Ab0Anx 


The  following  table  shows  the  percentages  of  the  various  oxides 
corresponding  to  each  feldspar  variety: 


Percentage  weights  of  the  oxides  in  the  feldspars  in  the  lime-soda  series. 


Si02. 

AI2O3. 

Na20. 

CaO. 

Albite.  Abi  Ano - 

68.7 

19.5 

11.8 

0.0 

Ab6  Am 

64.9 

22.1 

10.0 

3.0 

Ab3  Ani 

62.0 

24.0 

8.7 

5.3 

Abi  Ani 

65.6 

28.3 

5.7 

10.4 

Abi  An3 

49.3 

32.6 

2.8 

15.3 

Abi  An6 

46.6 

34.4 

1.6 

17.4 

Anorthite,  Abo  Ani 

43:2 

36.7 

.0 

20.1 

The  field  and  microscopic  studies  made  by  the  writer  and  the  few 
analyses  available  indicate  that  most  of  the  plagioclase  present  in 
feldspar  deposits  worked  for  pottery  purposes  belongs  to  the  sodic 
varieties,  albite  or  oligoclase,  though  the  more  calcic  varieties  are 
probably  also  present  in  minor  amounts  in  a few  localities.  In  color 
the  albite  and  oligoclase  range  from  pure  white  to  pale  green.  In 
their  commonest  forms  they  show,  as  do  the  feldspars  of  the  potash- 
soda  group,  two  principal  cleavage  faces  with  brilliant  luster,  but 
these  intersect  not  at  90°,  as  in  orthoclase  and  microcline,  but  at 
about  86°.  This  difference  in  angle  is  not  readily  recognizable  with- 
out careful  measurements,  and  in  the  field  albite  and  other  lime-soda 
feldspars  are  most  readily  distinguished  from  the  potash-soda  feld- 
spars by  the  presence  in  them  of  faint,  perfectly  straight  striations  on 
the  most  brilliant  of  the  cleavage  faces.  These  are  the  result  of 
repeated  twinning  of  the  crystal  and  are  best  seen  by  holding  the 
crystal  in  the  sunlight  so  as  to  catch  the  reflection  from  the  principal 
cleavage  face.  By  turning  the  crystal  slightly  one  way  or  another 
the  striations,  if  present,  are  readily  recognized. 

Pure  soda  feldspar,  or  albite  (NaAlSi308,  designated  Ab),  like 
potash  feldspar,  has  no  definite  melting  point  but,  as  shown  by  Day 
and  Allen,0  melts  at  temperatures  having  a range  of  150°  C.  or  more, 
certain  portions  of  a crystal  persisting  solid  while  other  portions  are 


a Day,  A.  L.,  and  Allen,  E.  T.,  loc.  cit. 


122  PEGMATITES  AND  ASSOCIATED  ROCKS  OF  MAINE. 

fluid.  Melting  in  a piece  of  natural  albite  was  observed  to  begin 
below  1,200°  C.  and  was  not  complete  at  1,250°.  Complete  fusion 
takes  place  in  albite  at  a somewhat  lower  temperature  than  in  ortho- 
clase  and  microcline.  Hence  in  the  manufacture  of  pottery  a glaze 
prepared  with  albite  will  become  fluid  and  will  run  at  a kiln  tempera- 
ture at  which  a potash-feldspar  glaze  remains  more  viscous  and 
yields  good  results. 

The  feldspars  of  this  class  that  contain  notable  amounts  of  calcium 
have  fairly  well  defined  melting  points.  These  melting  points,  as 
determined  by  Day  and  Allen,®  are  given  below,  with  the  determina- 
tions of  their  specific  gravity : 

Melting  temperature  and  specific  gravity  of  lime-soda  feldspars. 


Melting 

tempera- 

ture 

(°C.). 

Specific 
gravity 
of  crys- 
talline 
form. 

Albite,  Abi  Ano 

2. 605 

Ab3  Ani 

1,340 

1,367 

1,419 

1,463 

1,500 

2. 649 

Ab2  Ani 

2.  660 

Abi  Ani 

2. 679 

Abi  An2 

2.710 

Abi  An.5 

2. 733 

Anorthite,  Abo  Ani 

1,532 

2.  765 

As  shown  in  this  table  the  melting  points  become  progressively 
higher  and  the  minerals  become  heavier  with  increase  in  the  per- 
centage of  calcium. 

If  a melt  composed  solely  of  the  constituents  of  pure  potash  feld- 
spar or  pure  soda  feldspar  is  allowed  to  cool  the  result  is  invariably  a 
glass;  a crystalline  product  has  not  yet  been  obtained  in  this  way. 
If,  however,  melts  of  the  lime-rich  feldspars  are  cooled,  partial  or 
complete  crystallization  usually  takes  place.  It  is  this  property  of 
cooling  to  a glass  that  renders  the  potash  and  soda  rich  feldspars 
serviceable  for  use  in  making  glazes  for  pottery  and  enamelware. 
The  crystallization  that  takes  place  in  the  lime-rich  feldspars  under 
similar  conditions  makes  them  worthless,  or  at  least  much  less  desir- 
able, for  these  uses. 

The  following  analyses  show  the  chemical  characters  of  typical 
feldspars  that  are  used  commercially.  Most  of  the  specimens  of 
crude  material  analyzed  were  especially  selected  for  their  purity  and 
are  not  typical  of  the  material  in  commercial  use.  INI os.  5 and  6, 
however,  are  analyses  of  specimens  of  ground  “spar”  collected  by 
the  writer  personally  from  the  bins  at  feldspar  mills  and  represent 
materials  in  actual  commercial  use. 


a Day,  A.  L.,  and  Allen,  E.  T.,  loc.  cit. 


FELDSPAR. 


123 


Analyses  of  feldspars. 


Selected  specimens  of  crude 
feldspar. 

Commercial 
specimens  of 
ground  feldspar. 

1. 

2. 

3. 

4. 

5. 

6. 

Silica  (Si02)  

64  7 
18  4 

64.98 
19. 18 
.33 
Trace. 
.25 
12. 79 
2.32 

66.23 
18. 77 
Trace. 

.31 
None. 
12. 09 
3 11 

65. 95t 
18. 00 
.12 
1.05 
Trace. 
12.13 
2.11 

76. 37 
a 13. 87 

65.87 
a 19. 10 

Alumina  (AI2O1)  

Ferric  oxide  (Fe20s)  

Lime  (CaO)  

.26 
None. 
5. 24 
3. 74 
.30 

.20 
None. 
12. 24 
2. 56 
.64 

Magnesia  (MgO) 

Potash  (K2O) 

16.9 

Sndfl.  (Na.oOl  

Water  (H20)  

Loss  on  ignition  

.48 

100.0 

100  33 

100.  51 

99.36 

99. 78 

100. 61 

a Includes  trace  of  iron  and  any  TiC>2  and  P2O5  that  may  be  present. 

1.  Theoretical  composition  of  pure  orthoclase  or  microcline. 

2.  Specimen  of  crude  Norwegian  potash  feldspar,  probably  with  some  intergrown  soda  feldspar  (albite). 
Used  at  the  Royal  Porcelain  Works  at  Charlottenburg,  Sweden. 

3.  Crude  pink  orthoclase-microcline  feldspar,  evidently  intergrown  with  some  soda  feldspar  (albite). 
From  feldspar  quarry  of  Richardson  & Sons,  Bedford,  Ontario.  Analysis  by  J.  B.  Cochrane,  Royal  Mili- 
tary College,  Kingston,  Ontario. 

4.  Crude  pink  potash  feldspar;  microcline  intergrown  with  small  amounts  of  soda  feldspar  (albite). 
From  feldspar  quarry  of  P.  H.  Kinkles’s  Sons,  Bedford,  Westchester  County,  N.  Y.  Analyses  made  for 
John  C.  Wiarda  & Co. 

5.  Ground  commercial  feldspar  from  Kinkles’s  quarry,  Bedford,  N.  Y.;  so-called  No.  3 grade;  used  in 
glass  manufacture  but  not  for  pottery.  Sample  taken  by  writer  from  bins  at  mill  of  P.  H.  Kinkles’s  Sons. 
Analysis  by  George  Steiger,  in  laboratory  of  United  States  Geological  Survey. 

6.  Ground  commercial  feldspar  from  quarry  of  J.  B.  Richardson  & Sons,  Bedford,  Ontario,  No.  1 grade. 
Sample  taken  by  writer  from  bins  at  mill  of  Eureka  Flint  and  Spar  Company,  Trenton,  N.  J.  Analy- 
sis by  George  Steiger,  in  laboratory  of  United  States  Geological  Survey. 

The  approximate  mineral  composition  of  the  samples  of  the  com- 
mercial ground  feldspars  (Nos.  5 and  6),  as  computed  from  the 
analyses,  is  as  follows: 


Approximate  mineral  composition  of  feldspars  Nos.  5 and  6,  above. 


5. 

6. 

Quartz  (SiC>2) 

34. 37 

3. 84 

Potash  feldspar  (microcline  or  orthoclase)  (KAlSLOs) 

30.  58 

72.  28 

Soda  feldspar  (albite),  containing  some  lime  (NaAISLOs  and  CaALS^OO 

32. 83 

22.  59 

Moisture  (H2O) 

.30 

. 64 

Other  constituents 

1.63 

1.22 

99. 72 

100. 57 

Samples  Nos.  5 and  6 may  be  taken  to  represent,  so  far  as  the 
percentage  of  quartz  is  concerned,  the  two  extremes  among  potash 
“ spars”  in  commercial  use.  No.  5 is  much  richer  in  quartz  and  in 
soda  feldspar  than  the  higher  grades  from  this  same  quarry  and  is 
suitable  only  for  use  in  glass  making,  for  enamel  ware,  and  for  like 
uses.  No.  6 is  the  best  grade  of  Canadian  spar,  which  is  almost  free 
from  quartz  and  brings  as  high  a price  as  any  spar  on  the  market. 
The  bulk  of  the  No.  2 grade  or  standard  spar  that  is  on  the  market  is 
intermediate  in  its  percentage  of  quartz  between  samples  5 and  6, 
the  percentage  in  most  of  it  being  between  15  and  25  per  cent. 


124  pegmatites  and  ASSOCIATED  ROCKS  OF  MAINE. 

GRAPHIC  GRANITE. 

Much  of  the  quartz  and  feldspar  of  certain  pegmatite  deposits  is 
regularly  intergrown  in  the  form  of  graphic  granite.  (See  PI.  XVIII 
and  p.  22.)  At  the  majority  of  feldspar  quarries  most  of  the  material 
shipped  is  graphic  granite,  though  whatever  pure  feldspar  occurs  is 
usually  also  included  and  serves  to  raise  the  percentage  of  feldspar 
in  the  whole  mass.  Analyses  of  four  specimens  of  graphic  granite 
are  given  below.  These  analyses  were  made  by  George  Steiger  in  the 
laboratory  of  the  United  States  Geological  Survey. 

Analyses  of  graphic  granite. 


1. 

2. 

3. 

4. 

Si02 

73.89 

73. 92 
14. 26 

72. 76 
a 15. 47 

71.00 
a 16. 31 

13. 75 

.30 

FeO 

| .26 

MgO 

None. 

None. 

None. 

None. 

.22 

CaO 

None. 

None. 

.19 

2.35 

Na20 

2. 10 

2.06 

3.  44 

K20 

9.00 

8. 99 

9.28 

8.  66 

H20 

.24 

.11 

.15 

.12 

99. 24 

99. 64 

100.20 

99.75 

a Includes  trace  of  iron  and  any  Ti02  and  P2O5  that  may  be  present. 


1.  Coarse  graphic  granite  from  Fisher’s  feldspar  quarry  (abandoned),  Topsham,  Me.  Trace  of  P2O5. 
The  quartz  layers  in  this  specimen  average  about  0.1  inch  and  the  feldspar  layers  0.4  inch  across.  The 
feldspar  is  cream-colored  potash  feldspar  (microcline),  finely  (perthitically)  intergrown  with  smaller 
amounts  of  soda  feldspar  (albite). 

2.  Moderately  coarse  graphic  granite  from  Fisher’s  feldspar  quarry  (abandoned),  Topsham,  Me.  Grades 
into  No.  1.  Trace  of  P2O5.  The  quartz  layers  in  this  specimen  average  about  0.05  inch  across  and  the 
feldspar  layers  about  0.15  inch  across.  The  feldspars  are  of  the  same  character  as  in  No.  1. 

3.  Fine-grained  graphic  granite  from  Kinkles’  feldspar  quarry,  Bedford,  Westchester  County,  N.  Y. 
The  quartz  layers  in  this  specimen  average  about  0.03  inch  across  and  the  feldspar  layers  about  0.08  inch 
across.  The  feldspars  are  pale  pink  microcline  finely  intergrown  with  smaller  amounts  of  soda  feldspar 
(albite),  containing  a little  lime. 

4.  Graphic  granite  from  Andrews  quarry,  Portland,  Conn.,  varying  in  coarseness,  but  all  extremely  fine 
grained.  The  quartz  layers  in  this  specimen  average  not  more  than  0.02  of  an  inch  across  and  the  feldspar 
layers  not  more  than  0.05  inch  across.  Some  small  areas  of  pure  feldspar  were  associated  with  the  graphic 
granite  in  this  specimen,  so  that  the  silica  percentage  shown  in  the  analysis  is  lower  than  it  would  be  for 
graphic  granite  alone  of  this  fineness.  The  feldspars  are  white  potash  feldspar  (microcline),  intergrown 
witfi,  smaller  amounts  of  soda  feldspar  (albite),  containing  a little  lime. 

If  allowance  is  made  for  the  water  present  and  the  proportion  of 
quartz  to  feldspars  calculated  from  the  above  analyses,  the  results 
are  as  follows: 


Proportions  of  quartz  and  feldspar  in  graphic  granites  Nos.  1 to  4 above. 


1. 

2. 

3. 

4. 

Quartz  (Si Og)  - 

27.13 

54.42 

18. 45 
Trace. 

26. 26 
55. 22 

18.52 

Trace. 

22.94 

54.95 

20. 99 
1.12 

17.65 

51.37 

30.05 

.92 

Potash  feldspar  (microcline)  (KAlSisOs)  

Soda  feldspar  (albite)  with  small  amounts  of  lime  feldspar  in  Nos.  3 and 
4 (NaAlSi308,CaAl2Si204) 

Other  constituents 

100.00 

100.00 

100.00 

99. 99 

Note.— Nos.  1 and  2,  representing  graphic  granite  from  Fisher’s  quarry  in  Topsham,  Me.,  show  prac- 
tically identical  proportions  between  the  quartz  and  the  feldspar,  although  No.  2 is  more  than  twice  as 
coarse  as  No.  1.  In  No.  3,  from  Bedford,  N.  Y.,  soda-lime  feldspar  is  more  abundant  than  in  Nos.  1 and  2, 
and  the  proportion  of  quartz  is  slightly  less.  In  No.  4 some  pure  feldspar  is  associated  with  the  graphic 
intergrowth  of  feldspar  and  quartz,  so  that  the  proportion  of  quartz  in  the  whole  specimen  is  lower  than  in 
any  of  the  other  samples. 


U.  S.  GEOLOGICAL  SURVEY 


BULLETIN  445  PLATE  XVIU 


INTERGROWTHS  OF  FELDSPAR  AND  QUARTZ.  SHOWING  CHARACTERISTIC  GRAPHIC 
GRANITE  STRUCTURE.  NATURAL  SIZE. 


A,  Graphic  granite  from  Bedford,  N.  Y.  B,  Fine  graphic  granite  from  Topsham,  Maine.  C,  Coarse 
graphic  granite  from  Topsham,  Maine. 


FELDSPAR. 


125 


A graphic  intergrowth  of  potash  feldspar  and  quartz  from  Elfkarleo, 
Sweden,  which  was  so  fine  grained  that  the  graphic  structure  could 
be  seen  only  under  the  microscope,  showed  on  analysis  about  79.2 
per  cent  of  feldspar  and  20.8  per  cent  of  quartz.  From  the  analyses 
given  above  and  from  numerous  others  which  have  been  published 
the  conclusion  seems  justified  that  the  proportion  of  feldspar  to  quartz 
in  graphic  granites,  though  varying  somewhat  according  to  the  com- 
position of  the  feldspars,  is  nevertheless  fairly  constant  and  is  not 
dependent  on  coarseness  of  grain.  This  fact  is  of  practical  impor- 
tance, for  a large  proportion  of  the  commercial  “spar”  produced  is 
graphic  granite,  and  it  has  been  the  practice  at  some  quarries  to 
discard  the  finer-grained  varieties  on  the  supposition  that  they  con- 
tained a larger  percentage  of  quartz  than  the  coarser  kinds.  Such 
mining  practice  is  unwarranted,  the  fine  graphic  granite  being  as 
desirable  as  the  coarse,  though  both  should  be  mixed  with  a certain 
amount  of  pure  feldspar  in  order  to  reduce  the  percentage  of  quartz 
in  the  ground  product  to  between  15  and  20  per  cent  for  the  standard 
grade,  as  shown  by  analyses  3 and  4 of  the  table  above. 

As  in  most  pegmatite  bodies  there  is  very  little  regularity  in  the 
distribution  of  the  different  minerals  (see  p.  22),  a deposit  that  is  of 
excellent  quality  commercially  as  regards  feldspar  may  grade  within 
a short  distance  and  in  a wholly  irregular  manner  into  pegmatite  that 
is  worthless  because  of  its  large  percentage  of  quartz  or  its  abundance 
of  biotite,  black  tourmaline,  or  garnet. 

MINING. 

The  methods  of  mining  feldspar  are  very  simple.  The  excavations 
are  nearly  all  open  pits,  most  of  them  of  rather  irregular  form,  the 
valueless  portions  of  the  pegmatite  being  avoided  wherever  it  is  possi- 
ble in  mining.  In  a few  Pennsylvania  quarries  where  the  pegmatite 
masses  are  rather  flat  lying  and  are  overlain  by  a roof  of  worthless 
rock  short  tunnels  have  been  driven  from  the  open  pits. 

In  Maine,  Connecticut,  and  New  York  the  pegmatite  is  usually 
firm  and  undecomposed,  even  in  the  surface  outcrops,  and  it  is  neces- 
sary to  sink  drill  holes  and  blast  out  most  of  the  material.  In  Penn- 
sylvania and  Maryland,  however,  most  of  the  pegmatite  is  much 
decayed  at  the  surface  and  can  be  excavated  with  picks,  shovels,  and 
crowbars.  In  a few  of  these  quarries  kaolin  produced  by  the  decay 
of  the  feldspar  has  been  found  in  the  past  in  sufficient  quantities  to  be 
of  commercial  importance,  though  none  is  now  produced.  This  differ- 
ence in  the  character  of  the  pegmatite  deposits  in  the  two  regions  is  due 
to  the  fact  that  the  Pennsylvania-Maryland  region  is  unglaciated, 
whereas  in  the  more  northerly  region  glacial  ice  has  planed  off  most 
of  the  products  of  rock  decay. 


126  PEGMATITES  AND  ASSOCIATED  ROCKS  OF  MAINE. 

In  some  of  the  smaller  quarries,  wheye  the  rock  is  firm,  drilling  is 
done  by  hand,  but  in  most  of  the  larger  quarries  steam  drills  are  used. 
The  large  masses  are  then  broken  with  sledges  into  pieces  6 inches  or 
less  in  size.  If  the  material  is  to  be  used  as  poultry  grit  or  for  the 
manufacture  of  roofing  materials  no  sorting  is  necessary,  but  mate- 
rial used  for  making  pottery  is  hand-picked  at  the  quarry  to  remove 
the  more  micaceous  and  quartzose  parts  and  the  portions  carrying 
iron-bearing  minerals.  In  most  of  the  Pennsylvania  and  Maryland 
quarries  where  the  weathered  materials  near  the  surface  can  be 
excavated  with  pick  and  shovel,  screening  or  even  washing  may  be 
necessary  to  free  the  spar  from  dirt.  In  some  of  the  larger  and  deeper 
quarries  derricks  and  drags  are  used  in  hoisting  the  spar  to  the  surface, 
the  material  being  then  loaded  into  wagons  and  hauled  either  to  the 
railroad  for  shipment  or  to  the  mills  for  grinding.  In  some  quarries 
the  wagons  descend  into  the  pit  along  an  inclined  roadway.  At  two 
important  quarries  wire  tramways  connect  quarry  with  mill. 

The  cost  of  actual  mining  at  most  of  the  quarries  producing  feld- 
spar of  pottery  grade  is  reported  at  from  $2  to  $2.50  per  long  ton. 
At  certain  quarries  where  pegmatite  is  quarried  for  ready  roofing, 
poultry  grit,  etc.,  where  cobbling  and  hand  sorting  are  unnecessary, 
and  where  the  work  is  conducted  on  a large  scale,  the  cost  may  be  as 
low  as  50  cents  per  ton.  Hauling  by  team  from  mine  to  mill  or 
shipping  point  in  most  of  the  feldspar  districts  may,  under  ordinary 
conditions,  be  estimated  at  a contract  price  of  35  to  40  cents  per  long 
ton  per  mile. 

COMMERCIAL  AVAILABILITY  OF  DEPOSITS. 

Whether  it  will  pay  to  work  a given  feldspar  deposit  depends  upon  a 
number  of  factors,  chief  among  which  are  (1)  the  distance  from  the 
railroad  or  navigable  water,  (2)  the  freight  rates  to  principal  markets, 
(3)  the  quantity  and  quality  of  the  material  available,  (4)  the  cheap- 
ness with  which  the  feldspar  can  be  mined,  and  (5)  the  market  condi- 
tions. Favorable  conditions  with  respect  to  some  of  these  factors 
may  offset  unfavorable  conditions  with  respect  to  others.  The 
principal  markets  for  the  better  grades  of  feldspar  are  the  great  pottery 
centers — Trenton,  N.  J.,  and  East  Liverpool,  Ohio — so  that  the  mines 
of  Connecticut,  Pennsylvania,  and  Maryland  have  the  advantage  over 
those  in  Maine  and  northern  New  York  of  being  much  closer  to  these 
markets.  This  superiority  in  position  makes  wagon  hauls  of  6 or  8 
miles  from  mine  to  shipping  point  permissible  in  the  Middle  Atlantic 
States,  whereas  in  Maine  or  in  the  Adirondack  region  only  a much 
shorter  haul  allows  a fair  degree  of  profit.  Pegmatite  sold  for 
roofing  or  poultry  grit  commands  prices  so  small  that  hauls  of  more 
than  1 or  2 miles  from  mine  to  shipping  point  would  in  most  places  be 
prohibitive.  The  freight  rates  on  feldspar  from  a number  of  the 


FELDSPAR. 


127 


quarrying  districts  to  Trenton,  the  principal  feldspar  milling  center, 
are  given  below: 

Freight  rates  per  hundredweight  on  feldspar  for  carloads  having  a minimum  weight  of 40,000 

pounds , May,  1909. 


Bath,  Me.,  to  Trenton,  N.  J $0. 15 

Cathance,  Me.,  to  Trenton,  N.  J 17 

Auburn,  Me.,  to  Trenton,  N.  J 16 


The  requirements  of  the  potter’s  trade  demand  that  in  general  the 
percentage  of  free  quartz  associated  with  the  feldspar  used  shall  not 
exceed  20  per  cent  in  the  ground  product,  and  certain  potters  demand 
a spar  which  is  nearly  pure,  containing  probably  less  than  5 per  cent 
of  free  quartz.  In  order  to  be  profitably  worked,  in  most  feldspar 
mines  between  one-fourth  and  one-half  of  the  total  material  excavated 
should  contain  less  than  20  per  cent  of  free  quartz.  Freshness  of  the 
feldspar  is  not  essential. 

A factor  of  the  utmost  importance  in  the  mining  of  pottery  spar  is 
the  quantity  of  iron-bearing  minerals  (black  mica,  hornblende,  gar- 
net, or  black  tourmaline)  which  is  present  and  the  manner  in  which 
these  minerals  are  associated  with  the  feldspar.  The  requirements  of 
the  pottery  trade  demand  that  the  spar  be  nearly  free  from  these 
minerals,  which  if  present  produce,  upon  firing,  brown  discolorations  in 
white  wares.  In  order  that  a deposit  may  be  profitably  worked, 
these  minerals,  if  present  in  any  appreciable  quantity,  must  be  so 
segregated  in  certain  portions  of  the  deposit  that  they  can  be  sepa- 
rated from  the  spar  without  much  more  hand  sorting  and  cobbing 
than  is  necessary  in  the  separation  of  the  highly  feldspathic  material 
from  that  which  is  highly  quartzose  or  rich  in  muscovite.  A number 
of  pegmatite  deposits  of  coarse  grain  are  rendered  worthless  for  pot- 
tery purposes  by  the  abundance  of  one  or  more  of  these  iron-bearing 
minerals.  The  presence  here  and  there  of  minute  flakes  of  white 
mica  (muscovite)  is  characteristic  even  of  the  highest  grades  of  com- 
mercial feldspar,  and  chemically  this  mineral  is  not  injurious.  It  is, 
however,  exceedingly  difficult  to  pulverize  the  thin,  flexible  mica 
plates  to  a fineness  equal  to  that  attained  by  the  feldspar,  and  it  is 
therefore  necessary  in  mining  to  separate  carefully  as  much  of  the 
muscovite  as  possible  from  the  spar. 

Operation  on  a large  scale  with  the  aid  of  modern  machinery 
reduces  the  mining  cost.  Favorable  topographic  position — a situa- 
tion, for  instance,  that  will  permit  the  material  to  be  excavated 
from  a hillside  opening  instead  of  being  hoisted  from  a pit — also 
reduces  the  cost. 

MILLING. 

The  methods  used  for  grinding  feldspar  for  pottery,  enamel  ware, 
etc.,  are  similar  in  a general  way  in  all  of  the  Eastern  States  and 
are  very  simple.  The  soda  spar  quarried  in  southeastern  Pennsyl- 


128 


PEGMATITES  AND  ASSOCIATED  EOCKS  OF  MAINE. 


vania  is  first  burned  in  kilns,  which  serves  to  fracture  it  and  thus  to 
facilitate  grinding.  Most  feldspar,  however,  is  fed  just  as  it  comes 
from  the  quarry  into  a chaser  mill  consisting  of  two  buhrstone  wheels, 
3 to  5 feet  in  diameter  and  1 to  1J  feet  thick,  attached  to  each  other 
by  a horizontal  axle,  as  are  the  wheels  of  a cart.  The  horizontal 
axle  is  attached  at  its  center  to  a rotating  vertical  shaft,  which 
causes  the  buhrstone  wheels  to  travel  over  a buhrstone  bed,  the 
feldspar  being  crushed  between  the  wheels  and  the  bed.  In  a few 
mills  the  spar  before  going  to  the  chaser  mills  is  crushed  in  a jaw 
crusher. 

The  material  as  it  comes  from  the  chasers  is  screened,  the  tailings 
being  returned  to  the  chaser  mills  for  recrushing,  while  the  fines  go 
to  tube  mills  for  final  grinding.  The  tube  mills  consist  of  steel 
cylinders  revolving  on  a horizontal  axis.  The  cylinders  are  gener- 
ally lined  either  with  hard-wood  blocks  or  with  blocks  made  of 
natural  or  artificial  siliceous  brick  and  are  charged  with  Norway  or 
French  flint  pebbles  2 to  3 inches  across.  The  type  of  tube  mill 
used  by  most  feldspar  grinders  is  6 to  7 feet  long  and  grinds  from  2 
to  3 tons  of  spar  at  one  charging.  Certain  millers,  however,  claim 
to  effect  a considerable  saving  in  power  by  the  use  of  larger  mills, 
which  grind  from  4 to  6 tons  at  one  charge. 

Feldspar  for  pottery  purposes  is  usually  ground  four  to  six  hours, 
and  in  that  time  most  of  it  is  reduced  to  a fineness  of  less  than  200 
mesh.  Screen  tests  made  by  the  writer  on  four  samples  of  com- 
mercial ground  pottery  spar  collected  personally  from  the  bins  at 
three  feldspar  mills  showed  that  from  99.3  to  99.8  per  cent  of  the 
material  would  pass  through  a 100-mesh  screen  and  from  96.7  to 
98.2  per  cent  would  pass  through  a 200-mesh  screen.  A sample  of 
No.  3 spar,  used  only  in  making  glass  and  enamel  ware,  was  notably 
coarser,  94  per  cent  passing  through  a 100-mesh  screen,  and  74  per 
cent  through  a 200-mesh  screen.  This  grade  is  ground  only  for 
two  to  three  hours.  ' Some  feldspar  prepared  for  use  in  abrasive 
soaps  is  ground  for  ten  hours. 

After  grinding,  the  spar  is  ready  for  shipment  either  in  bulk  or  in 
bags.  The  red  spars  from  Bedford,  N.  Y.,  and  Bedford,  Ontario, 
have  a faint  pinkish  tint  when  ground,  but  the  cream-colored  and 
white  spars  grind  to  a pure  white.  In  a few  mills  the  ground  spar 
is  allowed  to  settle  slowly  in  water,  so  as  to  separate  the  finer  from 
the  coarser  material,  but  this  method  is  now  rarely  used. 

In  mills  for  grinding  feldspar  for  poultry  grit  and  roofing  purposes 
the  spar  is  first  crushed  in  jaw  or  rotary  crushers  and  then  between 
steel  rolls.  It  is  then  screened  over  vibrating  screens,  usually  of  the 
Newago  or  Jeffrey  type,  to  the  various  sizes  desired. 


FELDSPAR. 


129 


USES. 

The  principal  consumers  of  feldspar  are  the  pottery,  enamel-ware, 
enamel-brick,  and  electrical-ware  manufacturers,  its  most  important 
use  being  as  a constituent  part  of  both  body  and  glaze  in  true  porce- 
lain, white  ware,  and  vitrified  sanitary  ware,  and  as  a constituent 
of  the  slip  (underglaze)  and  glaze  in  so-called  “ porcelain”  sanitary 
wares  and  enameled  brick.  The  proportion  of  feldspar  in  the  body 
of  vitrified  wares  usually  falls  between  10  and  35  per  cent.  Its 
melting  point  being  lower  than  that  of  the  other  constituents,  it 
serves  as  a flux  to  bind  the  particles  of  clay  and  quartz  together. 
In  glazes  the  percentage  of  feldspar  usually  lies  between  30  and  50. 
The  trade  demands  that  feldspar  for  pottery  purposes  be  nearly 
free  from  iron-bearing  minerals  (biotite,  garnet,  hornblende,  tourma- 
line, etc.),  and  that  it  contain  little  if  any  muscovite.  The  require- 
ments in  regard  to  the  percentage  of  free  quartz  vary  with  different 
potters.  A few  manufacturers  of  the  finer  grades  of  pottery  demand 
less  than  5 per  cent  of  free  quartz  and  may  even  grind  the  spar 
themselves  so  as  to  be  sure  of  its  quality,  preferring  to  insure  a con- 
stant product  even  at  higher  cost  by  themselves  mixing  the  requisite 
quantity  of  quartz  with  the  spar.  Most  potters  get  satisfactory 
results  with  standard  ground  spar  carrying  15  to  20  per  cent  of 
free  quartz,  and  in  some  acceptable  spars  the  percentage  runs  even 
higher.  In  the  finely  ground  mixture  as  it  comes  from  the  mills  it 
is  difficult  to  separate  the  quartz  from  the  feldspar  by  physical 
methods  on  account  of  the  extreme  fineness  of  the  material.  Chem- 
ical analysis  seems  to  be  the  readiest  means  of  determining  whether 
its  percentage  is  high  or  low. 

Feldspar  is  also  used  in  the  manufacture  of  emery  and  carbo- 
rundum wheels  as  a flux  to  bind  the  abrading  particles  together. 

Small  quantities  of  feldspar  are  used  in  the  manufacture  of  opales- 
cent glass.  The  feldspar  used  for  this  purpose  is  ranked  as  No.  3 
by  the  miners.  This  generally  contains  more  free  quartz  and  mus- 
covite than  that  used  for  pottery  purposes,  and  most  of  it  contains 
also  fragments  of  iron-bearing  minerals.  Most  of  the  spars  known 
to  the  writer  which  are  used  for  opalescent  glass  are  rich  in  soda. 
They  are  not  ground  so  fine  as  the  pottery  spars  (p.  128). 

Small  quantities  of  carefully  selected  pure  feldspar  are  used  in  the 
manufacture  of  artificial  teeth.  Some  is  used  in  the  manufacture  of 
scouring  soaps  and  window  washes,  the  fact  that  feldspar  is  slightly 
softer  than  glass  rendering  these  soaps  less  liable  than  soaps  which 
contain  quartz  to  scratch  windows  or  glassware.  Two  firms  in  New 
York  State  and  one  in  Connecticut  crush  feldspar  for  poultry  grit 
and  for  the  manufacture  of  ready  roofing. 

63096°— Bull.  445—11 9 


130 


PEGMATITES  AND  ASSOCIATED  ROCKS  OF  MAINE. 


Much  interest  has  recently  been  aroused  in  the  use  of  potash  feld- 
spar as  a fertilizer.  Potash  is  an  important  plant  food,  which,  in 
fertilizers,  has  usually  been  supplied  in  the  form  of  wood  ashes  or 
imported  from  Germany  in  easily  soluble  potash  salts  (sulphate, 
carbonate,  or  chloride).  The  Department  of  Agriculture  has  recently 
made  preliminary  experiments  to  determine  the  availability  of  finely 
ground  potash  feldspar  as  a substitute  for  the  more  soluble  potash 
salts.  The  following  statement  is  quoted  from  the  report  on  these 
tests : a 

The  evidence  so  far  obtained  appears  to  indicate  that  under  certain  conditions  and 
with  certain  crops  feldspar  can  be  made  useful  if  it  is  ground  sufficiently  fine.  On 
the  other  hand,  it  is  highly  probable  that  under  other  conditions  the  addition  of 
ground  feldspar  to  the  land  would  be  a useless  waste  of  money.  At  the  present  stage 
of  the  investigation  it  would  be  extremely  unwise  for  anyone  to  attempt  to  use  ground 
rock,  except  on  an  experimental  scale  that  would  not  entail  great  financial  loss. 

If  further  experiment  shows  that  ground  feldspar  has  a wide 
efficiency  as  a fertilizer,  it  will  undoubtedly  lead  to  the  utilization 
of  many  of  the  pegmatite  deposits  which,  because  of  insufficient 
coarseness,  too  large  a percentage  of  quartz,  or  too  great  an  abun- 
dance of  iron-bearing  minerals,  are  not  valuable  as  a source  of  pottery 
material.  Deposits  of  this  kind,  favorably  situated  with  respect  to 
the  railroads,  are  numerous,  especially  in  the  vicinity  of  the  active 
feldspar  quarries.  An  equally  important  result  will  be  the  utiliza- 
tion of  much  material  that  is  now  discarded  at  feldspar  quarries. 

A number  of  processes  have  been  patented  in  this  country  for  the 
dissociation  of  potash  feldspar  to  obtain  the  more  readily  soluble 
potash  salts,  but  none  of  these  have  yet  been  successfully  applied  on 
a commercial  scale.  What  is,  perhaps,  the  most  promising  method 
effects  the  decomposition  through  electrolytic  methods.6 

GRADES  AND  PRICES. 

Most  dealers  recognize  three  grades  of  commercial  feldspar — No.  1, 
No.  2 (sometimes  called  standard),  and  No.  3.  From  quarries  in 
granite  pegmatite,  where  most  of  the  spar  is  of  the  potash  variety, 
these  are  usually  graded  as  follows:  No.  1 is  carefully  selected,  free 
from  iron-bearing  minerals,  largely  free  from  muscovite,  and  con- 
tains little  or  no  quartz,  usually  less  than  5 per  cent.  Analysis  6 of 
the  table,  on  page  123,  shows  the  character  of  material  of  this  grade, 
the  feldspar  analyzed  having  been  imported  from  Canada.  No.  2 is 


a Cushman,  Allerton  S.,  The  use  of  feldspathie  rocks  as  fertilizers:  Bull.  Bureau  Plant  Ind.  No.  104 
U.  S.  Dept.  Agr.,  1907,  p.  31. 

b Cushman,  A.  S.,  Extracting  potash  from  feldspar:  Min.  World,  June  22, 1907;  also  United  States  patent, 
No.  772612,  October  18,  1904. 


FELDSPAR. 


131 


largely  free  from  iron-bearing  minerals  and  muscovite,  but  usually 
contains  when  ground  from  15  to  20  per  cent  of  quartz.  No.  3 is  not 
carefully  selected  and  contains  a little  higher  percentages  of  quartz, 
muscovite,  and  iron-bearing  minerals.  Spar  from  the  soda  pegmatites 
of  southeastern  Pennsylvania  and  adjacent  parts  of  Maryland,  being 
wholly  free  from  quartz,  is  graded  entirely  on  the  basis  of  its  freedom 
from  iron-bearing  minerals,  principally  hornblende.  No.  1 is  care- 
fully selected  and  is  practically  free  from  such  impurities.  No.  2, 
though  less  carefully  selected,  is  still  fairly  free  from  them.  No.  3 is 
not  carefully  selected  and  carries  hornblende  in  quantities  large 
enough  to  render  it  unfit  for  use  in  the  manufacture  of  pottery.  It 
is  utilized  principally  in  making  glass.  Crushed  pegmatite  from 
New  York  State,  used  for  poultry  grit  and  for  coverings  for  surfaces 
to  give  them  the  appearance  of  granite,  and  feldspar  from  Minne- 
sota, used  mainly  for  abrasive  purposes,  are  graded  according  to 
coarseness. 

The  prices  of  feldspar  fluctuate  with  general  market  conditions 
and  local  conditions  of  competition,  but  in  general  are  about  as 
follows: 


Prices  of  feldspar  f.  o.  b.  mills. 


Crude,  per 
long  ton. 

Ground, 
per  short 
ton. 

Maine:  No.  2 or  standard . 

S2.  50-$3. 00 

Northern  New  York:  Crushed  pegmatite  for  ready  roofing,  poultry  grit,  etc 

Southern  New  York: 

No.  1 

No.  2 or  standard 

4. 24-  4.  50 
3. 50  4.00 

$3. 00- $3. 50 

8.50-  9.00 
0. 00-  6.  50 
5.  50-  6.  50 
7.  50-  9.  00 

Connecticut:  No.  2,  or  standard 

3.50  4.00 

Pennsylvania:  No.  2,  or  standard  (potash  feldspar) 

Maryland:  No.  2,  or  standard  (potash  feldspar) 

3.  50-  4. 00 

5.50 
5.00-  5.25 

Trenton,  N.  J.: 

No.  1,  Canadian 

10.50 
9.00-  9.50 

No.  2,  or  standard 

Crude  No.  1 feldspar  usually  brings  from  50  cents  to  $1.50  a ton 
more  than  No.  2,  and  crude  No.  3 brings  about  the  same  amount 
less.  Ground  No.  1 brings  from  $2  to  $4  a ton  more  than  No.  2. 
With  finer  grinding,  such  as  is  demanded  by  some  scouring-soap 
manufacturers,  the  prices  are  proportionally  higher.  Very  pure 
carefully  selected  potash  feldspar,  for  use  in  the  manufacture  of 
artificial  teeth,  usually  sells  at  from  $6  to  $8  a barrel  of  350  pounds. 


V 


132  PEGMATITES  AND  ASSOCIATED  ROCKS  OF  MAINE. 


PRODUCTION. 

The  tables  below  show  the  recent  production  of  feldspar  in  the 
United  States. 

Production  of  feldspar  {exclusive  of  abrasive  feldspar)  in  1907  and  1908,  by  States, 

in  short  tons. 


State. 

Crude. 

Ground. 

Total. 

Quantity. 

Value. 

Quantity. 

Value. 

Quantity. 

Value. 

1907. 

Maine . 

New  York 

Connecticut 

Pennsylvania 

Maryland 

Other  States 

1908. 

Maine 

New  York 

Connecticut 

Pennsylvania 

Maryland 

Virginia  and  Minnesota 

45 
3,909 
10, 663 
7,367 
7,169 
1,927 

$110 
15,825 
28,433 
28, 169 
23, 672 
5,607 

16,428 

11,500 

8,380 

12,266 

3,895 

1,000 

$157, 224 
40,500 
51,770 
108, 678 
34,081 
5,000 

16,473 

15,409 

19,043 

19,633 

11,064 

2,927 

$157,334 
56, 325 
80, 203 
136, 847 
57, 753 
10, 607 

31,080 

101,816 

53, 469 

397,253 

84,549 

499,069 

168 

504 

7,775 

3,616 

6,217 

560 

375 
1,350 
27, 753 
13,226 
21,076 
2,000 

13,751 
14, 109 
6,425 
10,473 
3,517 
125 

123,034 
51,798 
38, 506 
90,276 
30,774 
750 

13,919 

14,613 

14,200 

14,089 

9,734 

685 

123,409 
53, 148 
66, 259 
103,502 
51,850 
2,750 

18,840 

65.780 

48, 400 

335,138 

67, 240 

400, 918 

Total  production  of  feldspar  in  1907  and  1908,  in  short  tons. 


Crude. 

Ground. 

Total. 

Quantity. 

Value. 

Quantity. 

Value. 

Quantity. 

Value. 

Production  of  feldspar  (exclusive  of 

abrasive) in  1908 

Production  of  abrasive  feldspar  in 
1908 

18,840 

$65,780 

48, 400 
3,234 

$335,138 
27, 635 

67,240 
. 3,234. 

$400,918 

27,635 

Total  production  of  feldspar  in 

1908 

Total  production  of  feldspar  in  1907  . 

18,840 

31,080 

65,780 

101,816 

51,634 

60,719 

362,773 
457, 128 

70,474 

91,799 

428,553 
558, 944 

The  production  of  feldspar  (exclusive  of  abrasive  feldspar)  from 
1903  to  1908  is  given  in  the  following  table: 


Production  of  feldspar  {exclusive  of  abrasive  feldspar),  1903-1908,  in  short  tons. 


Year. 

Crude. 

Ground. 

Total. 

Quantity. 

Value. 

Quantity. 

Value. 

Quantity. 

Value. 

1903 

13,432 

$51,036 

28,459 

$205,697 

41,891 

$256, 733 

1904 

19,413 

66, 714 

25, 775 

199,612 

45, 188 

266,326 

1905 

14,517 

57, 976 

20, 902 

168,181 

35,419 

226, 157 

1906 

39, 976 

132,643 

32,680 

268,888 

72,656 

401,531 

1907 

31,080 

101,816 

53,469 

397,253 

84,549 

499,069 

1908 

18.840 

65, 780 

48,400 

335,138 

67,240 

400, 918 

PEGMATITES  AND  ASSOCIATED  ROCKS  OF  MAINE.  133 

QUARTZ. 

GENERAL  STATEMENT. 

Quartz,  the  most  abundant  of  all  minerals,  occurs  in  nature  in  a 
great  variety  of  forms  and  is  utilized  commercially  in  many  different 
ways.  Sand  consisting  mainly  of  quartz  is  used  for  building,  mold- 
ing, and  in  glass  and  pottery  manufacture.  Tripoli,  used  for  abra- 
sive purposes,  and  sandstone  and  quartzite,  used  for  building  and 
other  purposes,  are  also  composed  largely  of  quartz.  The  present 
discussion,  however,  deals  only  with  the  massive  crystalline  and 
gem  varieties  which  occur  in  the  pegmatite  deposits. 

Chemically  pure  quartz  is  an  oxide  of  silicon  of  the  formula  Si02. 
It  is  too  hard  to  be  scratched  with  a knife  and  will  itself  scratch 
glass.  It  is  generally  translucent  to  transparent  and  ranges  from 
colorless  to  dark  gray,  and  in  the  gem  varieties  from  amethyst  to 
pale  pink.  It  is  brittle  and  without  well-defined  cleavage,  fracturing 
irregularly  with  lustrous  glassy  surfaces.  Most  of  the  quartz  of  the 
pegmatites  occurs  in  large  pure  masses  without  crystal  outline. 
Quartz  with  crystal  form  js  developed  principally  in  the  pockets. 
The  form  of  most  of  the  crystals  is  that  of  a six-sided  prism  ter- 
minated by  an  equal  number  of  faces  forming  a pyramid.  The 
mineral  is  difficultly  fusible  and  is  unaffected  by  acids  under  ordi- 
nary conditions. 

MASSIVE  CRYSTALLINE  QUARTZ. 

Occurrence. — Massive  crystalline  quartz  is  usually  white,  but  some 
is  rose-colored  or  smoky.  It  occurs  in  veins  or  dikelike  masses, 
unmixed  with  other  minerals,  or  as  a constituent  of  pegmatite.  In 
the  latter  form  it  is  usually  produced  as  an  accessory  in  the  mining 
of  feldspar.  The  States  producing  massive  crystalline  (vein)  quartz 
in  commercial  quantity  in  1908  were  Connecticut,  Maryland,  New 
York,  Pennsylvania,  Wisconsin,  Tennessee,  Montana,  Colorado, 
and  Arizona.  Small  quantities  were  formerly  marketed  from  Maine, 
but  these  quarries  are  so  far  from  the  principal  markets  thet  there 
is  very  little  profit  in  handling  the  material.  Quartz  of  excellent 
grade  occurs  in  considerable  quantities  at  nearly  all  of  the  feldspar 
quarries  of  Maine  and  in  a few  is  saved,  though  not  shipped  regularly. 
It  is  allowed  to  accumulate  in  stock  piles  until  a favorable  sale  can 
be  made. 

The  Connecticut  localities  at  which  quartz  is  mined  were  described 
in  detail  in  the  writer’s  report  on  the  production  of  quartz  and 
feldspar  in  1907.®  The  quarries  of  Westchester  County,  N.  Y.,  have 
also  been  previously  described  by  the  writer.6 

Milling. — In  the  grinding  of  the  massive  forms  of  quartz  two  general 
processes  are  used,  the  wet  and  the  dry. 


a Mineral  Resources  U.  S.  for  1907,  pt.  2,  U.  S.  Geol.  Survey,  1908,  pp.  84G-847. 
b Bull.  U.  S.  Geol.  Survey  No.  315,  1907,  pp.  29U309. 


134 


PEGMATITES  AND  ASSOCIATED  ROCKS  OF  MAINE. 


In  the  wet  process  the  quartz  may  be  crushed  just  as  it  comes  from 
the  quarry,  or  it  may  first  be  highly  heated  in  kilns  and  then  fractured 
by  turning  upon  it  a stream  of  cold  water.  The  first  crushing  is 
effected  by  jaw  crushers,  or  if  the  quartz  has  previously  been  burned 
it  may  be  crushed  in  chaser  mills.  In  a few  mills  the  chasers  revolve 
in  wet  pans  and  are  periodically  stopped  to  allow  the  crushed  quartz 
to  be  shoveled  out.  After  crushing,  it  is  ground  in  “wet  pans”  pro- 
vided with  a pavement  of  flat-faced  quartz  or  quartzite  blocks  over 
which  move  several  large  blocks  of  similar  material,  the  crushed 
quartz  being  pulverized  between  these  blocks  and  the  pavement. 
The  grinding  in  wet  pans  usually  occupies  about  twenty-four  hours, 
the  load  ground  in  a single  pan  varying  from  1,200  to  1,800  pounds. 
From  the  wet  pans  the  pastelike  mass  of  quartz  and  water  is  drawn 
into  settling  troughs,  the  first  settlings  being  in  some  cases  returned  to 
the  pans  for  finer  grinding.  From  the  settling  troughs  it  is  shoveled 
out  upon  drying  floors  heated  by  steam  or  hot  air,  or  else  it  is  dried 
in  small  pans  which  are  placed  tier  on  tier  on  heated  racks  constructed 
of  steam  pipes.  Finally  the  dried  material  is  bolted  to  various  degrees 
of  fineness  and  packed  in  bags  for  shipment,  or  it  may  be  .^hipped,, 
in  bulk. 

In  the  dry  method  of  treatment  the  quartz  is  usually  crushed  first 
in  a jaw  crusher  and  then  between  crushing  rolls.  Quartz  to  be  used 
for  filters  and  for  abrasive  purposes  is  then  screened  to  various  degrees 
of  fineness  and  is  packed  in  bags  for  shipment.  In  the  manufacture 
of  the  finer  grades  for  use  in  pottery,  wood  fillers,  scouring  soaps,  etc., 
the  material  after  leaving  the  roll  crushers  is  ground  in  tube  mills, 
either  of  the  continuous  or  of  the  intermittent  type.  It  is  then 
graded  to  various  sizes  either  by  bolting  or  by  a pneumatic  process 
whereby  the  quartz  powder  is  carried  by  a strong  air  current  through 
a series  of  tubes  and  receptacles,  the  distance  to  which  the  quartz 
is  carried  being  dependent  upon  its  fineness.  There  are  no  quartz 
mills  in  Maine.  Those  nearest  to  that  State  are  in  Connecticut. 

JJses. — Quartz  is  used  for  a great  variety  of  purposes,  the  principal 
uses  being  in  the  manufacture  of  wood  filler,  pottery,  paints,  and 
scouring  soaps.  In  pottery  the  quartz  serves  to  diminish  shrinkage 
in  the  body  of  the  ware;  it  is  used  also  in  many  glazes.  Quartz  for 
these  purposes  should  contain  in  general  less  than  one-half  of  1 per 
cent  of  iron  oxide.  Finely  ground  quartz  is  used  in  paints  in  various 
proportions  up  to  one-third  of  the  total  pigment  used.  Its  chemical 
inertness  prevents  it  from  combining  with  other  constituents  of  the 
paint  and  increases  the  resistance  of  the  paint  to  the  weather.  Crys- 
talline quartz  is  superior  to  silica  sand  for  this  purpose  because  the 
ground  particles  are  highly  angular  and  tend  to  attach  themselves 
more  firmly  to  the  painted  surfaces,  thus  giving  the  paint  what  is 
known  as  a “tooth”  and  after  some  wear  affording  a good  surface 


QUARTZ. 


135 


for  repainting.  This  angularity  of  the  grains  also  renders  the  ground 
crystalline  quartz  superior  to  silica  sand  in  the  manufacture  of  wood 
fillers.  In  scouring  soaps  and  polishers  ground  crystalline  quartz  is 
preferred  to  silica  sand,  not  only  because  of  its  greater  angularity, 
but  because  of  its  superior  whiteness. 

Massive  quartz,  crushed  and  graded  to  various  degrees  of  fineness, 
is  extensively  used  in  sandpaper,  sand  belts,  scouring  agents,  sand 
blasts,  etc.  The  qualities  which  render  it  particularly  serviceable  for 
these  purposes  are  its  hardness  (No.  7 in  the  Mohs  scale),  which  is 
slightly  greater  than  that  of  steel,  and  its  conchoidal  fracture,  the 
absence  of  definite  cleavage  planes  causing  it  to  crush  to  fragments 
with  sharp  angular  edges  and  corners.  For  such  abrasive  purposes 
massive  quartz  is  far  superior  to  sand  or  crushed  sandstone,  since 
the  grains  of  the  latter  are  likely  to  be  more  or  less  rounded.  Blocks 
of  massive  quartz  and  quartzite  are  used  in  the  chemical  industry  as 
a filler  for  acid  towers  and  to  some  extent  as  a flux  in  copper  smelting. 
Much  ground  quartz  is  used  in  filters,  and  some  of  the  most  finely 
pulverized  grades  are  used  in  tooth  powders  and  in  place  of  pumice 
as  a cleaner  by  dentists. 

Within  recent  years  crystalline  quartz  and  also  sand  has  been  used 
to  some  extent  in  the  manufacture  of  silicon  and  of  alloys  of  silicon 
with  iron  (ferrosilicon),  copper  (silicon  copper),  and  other  metals. 
Ferrosilicon  is  largely  produced  in  the  electric  furnace  by  using  coke 
to  reduce  the  quartz  to  the  metallic  state,  and  some  iron  ore  or  scrap 
iron  to  alloy  with  the  silicon.  The  percentage  of  silicon  in  these 
alloys  varies  from  about  10  to  80  per  cent,  according  to  the  uses  of 
the  product.  Ferrosilicon  has  been  employed  in  the  manufacture  of 
steel  as  a deoxidizer  and  to  prevent  the  formation  of  blowholes  in 
steel  ingots.  Silicon  is  also  produced  hi  the  electric  furnace.®  It  is 
a brittle  crystalline  body  with  a dark  silver  luster.  Its  specific  gravity 
is  about  2.4  and  its  melting  point  1,430°  C.  The  commercial  product 
contains  small  percentages  of  iron,  carbon,  and  aluminum.  The 
great  affinity  of  silicon  for  oxygen  renders  it  useful  for  the  reduction 
of  metals  such  as  chromium  and  tungsten  in  the  electric  furnace.  It 
can  readily  be  cast  into  rods,  and  because  of  its  high  electrical  resist- 
ance, which  is  about  five  times  that  of  carbon,  it  is  used  in  the  manu- 
facture of  rheostats  and  electrical  heaters.  Its  resistance  to  nearly 
all  acids,  combined  with  the  fact  that  it  can  be  cast  into  molds,  makes 
it  possible  also  to  use  it  in  the  manufacture  of  chemical  ware.  Silicon 
copper  is  used  as  a deoxidizer  in  making  castings  of  copper  and  copper 
alloys. 

Quartz  may  be  fused  in  the  electric  furnace  and  molded  into  tubes, 
crucibles,  dishes,  and  other  articles  which  can  be  used  for  certain 


o-  Tone,  F.  J.,  Production  of  silicon  in  the  electric  furnace:  Trans.  Am.  Electro-Chem.  Soc.,  vol.  7,  1905, 

p.  243. 


136 


PEGMATITES  AND  ASSOCIATED  ROCKS  OF  MAINE. 


purposes  in  the  chemical  laboratory  instead  of  porcelain  and  platinum 
wares.  The  fused  quartz  expands  only  very  slightly  when  heated, 
its  coefficient  of  expansion  being  about  one-twentieth  of  that  of  glass, 
and  in  consequence  may  be  plunged  suddenly,  red  hot,  into  cold  water 
without  being  cracked.  These  wares  soften  only  above  1,400°  C. 
(2,552°  F.).  The  principal  drawback  to  their  use,  especially  in 
quantitative  chemical  work,  is  that  the  somewhat  rough  surface  makes 
it  difficult  to  wash  all  the  material  from  the  dishes. 

Production. — Statistics  showing  the  production  of  quartz  in  the 
United  States  are  given  below. 


Production  of  quartz  ( exclusive  of  abrasive  quartz)  in  the  United  States  in  1908,  by  States, 

in  short  tons. 


State. 

Crude. 

Ground. 

Total. 

Quantity. 

Value. 

Quantity. 

Value. 

Quantity. 

Value. 

1908. 

Connecticut  and  New  York 

Pennsylvania  and  Maryland 

Other  States  a 

980 

25 

22, 500 

1,750 

QQ 

30, 594 

9,227 

4,160 

1,933 

56, 700 
31,670 
17,833 

10, 207 
4,185 
24,433 

58,450 

31,769 

48,427 

23, 505 

32,443 

15,320 

106, 203 

38,825 

138,646 

a Includes  Arizona,  Colorado,  Montana,  Tennessee,  and  Wisconsin. 


Abrasive  quartz  was  produced  in  1908  in  Connecticut,  Maryland, 
Massachusetts,  New  York,  Pennsylvania,  and  Wisconsin.  The  total, 
together  with  the  total  production  of  all  quartz,  is  shown  in  the 
following  table : 


Total  production  of  quartz  in  1908,  in  short  tons. 


Crude. 

Ground. 

Total. 

Quantity. 

Value. 

Quantity. 

Value. 

Quantity. 

Value. 

Quartz  (exclusive  of  abrasive  quartz) 
Abrasive  quartz 

23,505 

2,973 

$32,443 

4,876 

15,320 

5,518 

$106,203 

46,635 

38,825 

8,491 

$138,646 

51,511 

26,478 

37,319 

20,838 

152,838 

47,316 

190,157 

Production  of  quartz  (exclusive  of  abrasive  quartz ) in  tlte  United  States,  1903-1908,  in 

short  tons. 


Year. 

Crude. 

Ground. 

Total. 

Quantity. 

Value. 

Quantity. 

Value. 

Quantity. 

Value. 

1903 

40,046 

41,490 

39,555 

41,314 

5,618 

23,505 

$38,736 

28,890 

33,409 

37,632 

4,282 

32,443 

15,187 
10,780- 
il, 590 
25,383 
17,359 
15,320 

$118,211 

71.700 

70.700 
205,380 
152,812 
106, 203 

55,233 

52,270 

51,145 

66,697 

22,977 

38,825 

$156,947 

100,590 

104,109 

243,012 

157,094 

138,646 

1904 

1905 

1906 

1907 

1908 

QUARTZ. 


137 


Prices. — Pure  crystalline  quartz  for  use  in  the  manufacture  of 
pottery,  abrasive  soaps,  paints,  wood  fillers,  etc.,  brings  usually  from 
about  $2  to  $3.50  per  long  ton,  crude,  f.  o.  b.  quarries,  and  the  ground 
material  brings  from  $6.50  to  $10  per  short  ton  f.  o.  b.  mills,  the  price 
varying  with  fineness  of  grinding,  distance  from  markets,  etc.  The 
purer  varieties  of  quartzite  used  for  similar  purposes  and  for  sand- 
papers sell,  as  a rule,  at  somewhat  lower  prices,  the  crude  bringing 
from  about  $1  to  $2  per  long  ton  f.  o.  b.  mines,  and  the  ground  from  $6 
to  $8  per  short  ton  f.  o.  b.  mills.  The  finest  grades  of  crystalline 
quartz  ground  to  an  impalpable  powder  and  used  for  tooth  powders, 
etc.,  may  bring  as  high  as  $20  per  ton  f.  o.  b.  mills.  Imported  French 
flints  cost  from  $3.50  to  $4  per  long  ton  f.  o.  b.  Philadelphia,  and  can 
be  delivered  in  Trenton,  N.  J.,  for  less  than  $5  per  long  ton. 

SMOKY  QUARTZ. 

Smoky  quartz  has  somewhat  the  appearance  of  smoked  glass, 
though  varying  from  a faint  tint  of  gray  or  yellowish  brown  to  nearly 
black.  The  shade  commonly  varies  considerably  from  point  to  point 
in  the  same  crystal. 

Transparent  crystals  have  been  found  in  a number  of  the  pegmatite 
masses  of  Maine  and  some  are  of  value  as  museum  specimens  and  as 
gems.  In  1884  a mass  weighing  over  6 pounds,  with  clear  spaces 
several  inches  across,  was  found  on  Blueberry  Hill  in  the  town  of 
Stoneham,  Oxford  County,  and  a broken  crystal  that  weighed  over 
100  pounds  and  another  4 inches  long  and  2 inches  across,  very  clear 
in  parts,  were  found  near  Mount  Pleasant  in  Oxford  County.  On  the 
southwestern  slopes  of  Mount  Apatite  in  Auburn,  Androscoggin 
County,  a large  pocket  in  coarse  pegmatite  has  yielded  considerable 
quantities  of  fine  crystals.  Transparent  quartz  of  pale  amber-brown 
color  has  been  observed  by  the  writer  at  the  Berry  quarry,  a short 
distance  south  of  Mount  Apatite  in  Poland,  one  mass  showing  a clear 
portion  3 by  5 inches' in  size. 

The  nature  of  the  coloring  matter  is  not  known,  but  on  heating  the 
smoky  varieties  generally  become  first  yellow  and  finally  colorless. 
Some  yellow  quartz  produced  in  this  way  is  cut  as  a gem  under  the 
name  of  “Spanish  topaz”  or  “citrine,”  though  the  true  citrine  is  a 
natural  occurrence  of  transparent  yellow  quartz.  Crystals  or 
irregular  masses  of  transparent  smoky  quartz  found  in  any  of  the 
feldspar  or  gem  quarries  should  be  preserved,  for  they  may  prove  of 
value  and  interest  to  the  mineral  ot  gem  collector. 

ROSE  QUARTZ. 

Most  of  the  rose  quartz  found  in  Maine  is  somewhat  paler  in  tint 
than  that  commonly  utilized  as  a gem  stone,  though  occasionally 
some  of  deeper  tint  is  obtained.  The  principal  supplies  of  this  mate- 


138  PEGMATITES  AND  ASSOCIATED  ROCKS  OF  MAINE. 

rial  at  present  come  from  South  Dakota  and  Colorado.  In  Maine  it 
forms  irregular  masses  in  the  pegmatite  and  usually  grades  into  white 
quartz*  it  has  not  been  found  in  distinct  crystals.  It  occurs  in  a num- 
ber of  the  smaller  pegmatite  bodies  of  Oxford  County,  notably  at 
Tubbs  Ledge  in  Norway,  Frenchs  Mountain  in  Albany,  and  occasion- 
ally at  Mount  Mica  in  Paris,  but  so  far  as  known  very  little  has  been 
marketed.  In  a few  places  the  pale-rose  varieties  show  a milky 
opalescence  and  are  very  beautiful  when  well  polished. 

Rose  quartz  from  the  Red  Rose  mine  in  South  Dakota  is  reported 
to  have  sold  in  1908  at  from  3 to  25  cents  per  pound,  according  to 
depth  of  color  and  number  of  flaws  or  seams.  Selected  material 
brought  from  $8  to  $12  per  pound. 

AMETHYST. 

Amethystine  quartz,  or  amethyst  as  it  is  commonly  called,  is  a trans- 
parent purple  or  violet  variety  of  quartz  and  is  one  of  the  semiprecious 
stones.  It  must  not  be  confused  with  the  oriental  amethyst,  which  is  a 
rare  purple  variety  of  corundum  and  is  much  more  precious.  Deer 
Hill  in  the  extreme  northwestern  part  of  the  town  of  Stow,  Oxford 
County,  has  furnished  large  numbers  of  amethyst  crystals,  but 
nearly  all  of  them  are  of  a pale  tint  and  of  little  value  as  gems.  They 
occur  in  pockets  in  the  coarse  pegmatite  and  also  in  the  soil  on  the 
southeast  slope  of  the  hill,  where  the  pegmatite  is  associated  in  a most 
irregular  manner  with  fine-grained  granite.  Recently  George  HowTe, 
of  Norway,  Maine,  has  found  some  remarkably  fine  specimens  of  ame- 
thyst on  Pleasant  Mountain,  in  the  town  of  Denmark,  Oxford  County. 
By  transmitted  daylight  these  stones  are  a deep  royal  purple,  but  by 
lamplight  they  are  a rich  wine  red. 

As  in  the  case  of  most  other  Maine  gems,  the  retail  prices  obtained 
within  the  State  for  Maine  amethysts  are  considerably  higher  than 
those  prevailing  in  the  New  York  market.  They  range  up  to  $10  a 
carat  for  well-cut  stones  of  the  paler  varieties,  and  from  $10  to  $18 
a carat  for  those  showing  the  deep  colors. 

MICA. 

Types. — Mica  is  a group  name  comprising  a number  of  mineral 
species,  the  most  important  of  which,  economically,  are  biotite  (brown 
mica),  muscovite  (white  mica),  phlogopite  (amber  mica),  and  lepi- 
dolite  (pink  or  lilac  mica).  Though  biotite  is  occasionally  ground  for 
commercial  purposes,  it  is  so  intimately  intergrown  with  other  con- 
stituents in  the  Maine  pegmatites  as  to  be  unavailable  even  for  such 
treatment.  Lepidolite  from  Mount  Mica,  usually  intergrown  with 
some  albite  feldspar,  has  been  cut  into  slabs  and  polished  for  paper 
weights,  and  has  also  been  used  to  some  extent  as  a source  of  lithium 


U.  S.  GEOLOGICAL  SURVEY 


BULLETIN  445  PLATE  XIX 


MUSCOVITE  FROM  TOPSHAM,  SHOWING  WEDGE  STRUCTURE. 
A,  Front  view.  B , Side  view.  C,  End  view.  Natural  size. 


MICA. 


139 


salts;  its  use,  however,  is  sporadic  and  it  commands  no  steady  market 
price.  Phlogopite,  which  is  produced  in  large  quantities  in  Canada 
and  is  used  for  the  same  purpose  as  muscovite,  is  not  found  in  com- 
mercial amounts  in  the  United  States.  Muscovite  is  the  only  mica 
variety  of  commercial  importance  produced  in  Maine. 

Physical  and  chemical  properties. — Muscovite  is  a hydrous  silicate 
of  alumina  and  potash  with  a little  water  and  usually  a little  iron. 
The  hardness  of  the  mineral  is  between  2 and  3;  that  is,  mica  is  gen- 
erally soft  enough  to  be  scratched  with  the  finger  nail.  It  is  prac- 
tically infusible  at  ordinary  temperatures.  The  color  is  usually  a 
silver  gray  or  light  yellow,  and  the  mineral  is  generally  transparent. 
It  is  attacked  with  difficulty  by  reagents  and  in  nature  successfully 
resists  decomposition  for  long  periods.  Few  minerals  are  so  widely 
distributed.  In  small  flakes  it  is  a common  constituent  of  a great 
variety  of  rocks,  but  in  large  crystals,  such  as  can  be  used  commer- 
cially, it  is  generally  confined  in  Maine,  as  elsewhere,  to  pegmatite 
deposits.  Its  most  striking  physical  characteristic  is  its  highly  perfect 
basal  cleavage,  which  causes  it  to  split  into  tough,  flexible  sheets  whose 
thickness  may  be  less  than  a thousandth  of  an  inch.  The  crystals  as 
they  occur  in  the  pegmatite  thus  resemble,  in  a rough  way,  thick  pads 
of  paper  or  books.  The  name  “ books”  is,  indeed,  frequently  used 
in  the  trade  as  a convenient  descriptive  term  for  the  mica  crystals. 
A few  of  the  books  show  regular  hexagonal  borders,  but  as  a rule  their 
outlines  are  irregular. 

Muscovite  may  exhibit  certain  characteristics  not  mentioned 
above,  which  may  seriously  affect  its  commercial  value.  These  may 
be  enumerated  as  follows: 

By  far  the  commonest  defect  noted  in  the  muscovite  of  the  Maine 
pegmatites  is  what  is  usually  termed  A structure.  This  appears  to 
be  due  to  a wedging  out  of  the  mica  folia  in  two  directions  inclined 
to  each  other  at  60°.  It  is  recognized  in  a mica  book  by  the  presence 
of  two  sets  of  striations  at  60°  to  each  other  and  parallel  to  the  direc- 
tions of  the  “ ruling.”  In  most  of  the  Maine  quarries  such  A structure 
is  repeated  by  twinning  with  the  production  of  what  is  commonly 
.termed  “ fish-bone”  or  “herring-bone”  structure  (PI.  XIX).  Mus- 
covite showing  A and  fish-bone  structure  is  generally  used  only  as 
scrap  mica.  The  material  obtained  at  the  Black  Mountain  mine 
in  Rumford  was  wholly  of  this  type,  and  material  showing  these 
characters  is  found  in  nearly  all  the  pegmatite  deposits  which  have 
been  worked  commercially  either  for  feldspar,  mica,  or  gems,  and 
even  in  deposits  where  good  plate  mica  is  also  found. 

A second  defect  frequently  met  is  commonly  termed  “ruling” 
and  consists  in  the  presence  of  sharp,  straight  fractures  parallel  to 
the  sides  of  the  crystal  and  thus  highly  inclined  to  the  plates.  These 
are  in  fact  the  secondary  or  less  perfect  cleavage  directions  and 


140 


PEGMATITES  AND  ASSOCIATED  BOCKS  OE  MAINE. 


they  commonly  divide  a mica  mass  into  a number  of  long  narrow 
ribbon-shaped  strips.  Many  large  clear  books  which  otherwise  could 
be  cut  into  large  pieces  of  mica  are,  because  of  this  ruling,  rendered 
no  more  valuable  than  much  smaller  books  which  are  free  from 
this  defect.  In  some  crystals  instead  of  actual  cleavage  there  is  a 
folding  or  wrinkling  of  the  mica  laminae  parallel  to  the  secondary 
cleavage  directions,  which  suggests  that  both  wrinkling  and  actual 
cleavage  may  be  developed  in  some  cases  as  the  result  of  strains  to 
which  the  mica  books  have  been  subjected.  In  specimens  from  the 
Hibbs  mine  in  Hebron  the  secondary  cleavage  has  produced  a mul- 
titude of  fractures  so  close  together  that  their  intersection  with  the 
principal  cleavage  planes  reduces  the  mica  to  a mass  of  fine  fibers. 

Plate  mica  which  might  otherwise  be  of  good  quality  is  sometimes 
injured  by  the  presence  between  the  laminae  of  thin  crystals  of  mag- 
netite and  other  minerals  usually  showing  more  or  less  regular  radi- 
ating or  dendritic  forms.  Some  of  the  crystals  of  magnetite  occur- 
ring in  this  way  are  so  extremely  thin  that  they  are  transparent. 
The  presence  of  these  magnetite  crystals  injures  the  mica  for  elec- 
trical insulating  purposes,  as  .they  form  a path  for  the  current  and 
may  lead  to  a puncturing  of  the  plate  and  short-circuiting.  Some 
such  mica  is,  nevertheless,  used  to  some  extent  in  the  electrical 
industries.  .•  * - 

Perfectly  colorless  mica  bears  the  highest  value,  though  a slight 
tinge  of  color  is  for  most  purposes  not  regarded  as  a defect. 

Occurrence. — In  some  places,  as  at  the  Waterford  quarries  and 
Black  Mountain  mica  mine  in  Rumford,  Oxford  County,  the  mus- 
covite is  more  or  less  evenly  distributed  throughout  the  coarser  por- 
tion of  the  pegmatite  mass.  At  Black  Mountain  it  is  all  of  the 
wedge  variety,  some  of  the  spatulate  mica  books  being  3 feet  in 
length  and  1J  feet  in  maximum  width.  In  most  localities,  however, 
though  present  to  some  extent  in  all  parts  of  the  pegmatite  mass, 
muscovite  is  much  more  abundant  along  certain  zones.  The  com- 
monest mode  of  occurrence  is  illustrated  in  Plate  IX,  A,  and  has 
been  described  on  page  26.  More  or  less  rounded  aggregates  of  small 
muscovite  plates  occurring  in  certain  feldspar  quarries  have  also 
been  described  (p.  115).  At  the  Hibbs  mica  and  feldspar  mine  in 
Hebron,  muscovite,  mostly  of  the  wedge  variety,  occurs  sparingly 
throughout  the  whole  pegmatite  mass,  but  the  plate  mica  is  almost 
wholly  confined  to  a zone  3 to  4 feet  in  width  along  the  southwest 
wall  of  the  pegmatite  body.  It  makes  up  about  10  per  cent  of  this 
zone,  the  other  minerals  being  feldspar  and  quartz.  The  books  are 
variously  oriented;  some  of  them  have  a width  of  30  inches,  though 
the  average  is  about  5 inches. 

Mica  is  not  now  being  mined  in  Maine  and  the  efforts  to  mine  it  in 
the  past  have  for  the  most  part  proved  unprofitable  because  of  the 


MICA. 


141 


Small  amount  or  poor  quality  of  the  material  obtainable  as  com- 
pared with  other  mica-producing  districts.  It  seems  probable  that 
a few  of  the  Maine  deposits  could  be  worked  in  a small  way  with 
profit,  but  the  industry  can  never  be  of  much  magnitude  unless 
there  is  a marked  increase  in  the  demand  for  scrap  mica.  Localities 
where  it  has  been  mined  are  Albany,  Hebron,  Peru,  Black  Mountain 
in  Bumford,  and  Waterford,  all  in  Oxford  County.  The  mines  are 
described  in  the  locality  descriptions.  Deposits  of  mica  have  been 
found  in  about  twenty  States  of  the  United  States,  and  have  been 
worked  profitably  in  a number  of  them.  Among  the  States  where 
mica  ha3  been  actively  mined  are  North  Carolina,  South  Dakota, 
New  Hampshire,  Colorado,  Virginia,  Alabama,  South  Carolina, 
Idaho,  and  New  Mexico. 

Mining  and  manufacture. — The  mica  mining  at  the  Hibbs  mine 
in  Hebron  is  accessory  to  the  mining  of  feldspar,  both  minerals  being 
loosened  by  hand  drilling,  succeeded  by  blasting.  At  the  Black 
Mountain  mine  in  Rumford  the  material,  which  was  all  scrap  mica, 
was  loosened  by  steam  drilling  and  blasting  and  was  then  picked 
over  so  as  to  free  it  entirely  from  fragments  of  quartz  or  feldspar  or 
other  minerals.  It  was  then  placed  in  100-pound  bags,  hauled  to  the 
railroad,  and  shipped  to  Gildersleeve,  Conn.,  for  grinding. 

At  the  Beach  Hill  mine  in  Waterford  the  mica,  after  being  thor- 
oughly cleaned  of  adhering  matter,  was  split  up  with  a stout  knife 
into  plates  averaging  about  one-sixteenth  of  an  inch  in  thickness. 
If  these  plates  showed  fractures  or  creases  they  were  then  cut  into 
two  or  more  pieces,  the  knife  following  the  cracks  or  creases  so  as  to 
eliminate  the  imperfections  and  at  the  same  time  leave  as  large  per- 
fect plates  as  possible;  this  process  is  known  as  thumb  trimming. 
Most  of  the  plate  mica  was  marketed  in  this  form,  though  some  of 
the  output  was  further  trimmed  to  various  standard  market  sizes. 

Uses. — The  following  account  of  the  uses  of  mica  is  quoted  from 
a report  by  Douglas  B.  Sterrett:a 

The  principal  use  for  mica  during  recent  years  has  been  and  still  is  in  the  manu- 
facture of  electrical  apparatus;  formerly  its  application  in  stove  manufacture  con- 
sumed the  bulk  of  the  production.  The  glazing  industry  still  consumes  much  of  the 
finest  grades  of  sheet  mica  in  the  manufacture  of  windows  for  coal,  gas,  and  oil  stoves, 
gas-lamp  chimneys,  and  in  many  minor  uses,  as  lamp  shades,  fronts  for  fancy  boxes, 
etc.  The  use  of  mica  as  an  insulating  material  in  electrical  apparatus  and  machinery 
is  extensive.  Many  forms  of  dynamos,  motors,  induction  apparatus  using  high  voltage, 
switchboards,  lamp  sockets,  etc.,  have  sheet  mica  in  their  construction.  For  prac- 
tically every  purpose  of  electrical  insulation,  with  the  exception  of  commutators  of 
dynamos  and  motors,  the  domestic  mica  is  as  satisfactory  as  any  other.  For  insula- 
tion between  the  copper  bars  of  commutator  segments,  however,  no  mica  produced  in 
the  United  States  is  as  satisfactory  as  the  “amber”  or  phlogopite  mined  in  Canada  and 
Ceylon.  This  is  due  to  the  fact  that  the  “amber”  mica  wears  down  evenly  with  the 
copper  segments,  while  the  ordinary  white  or  muscovite  mica,  through  its  greater  hard- 
ness, does  not  wear  down  so  rapidly  and  is  left  in  ridges  above  the  copper,  causing  the 


a Mineral  Resources  U.  S.  for  1908,  pt.  2,  U.  S.  Geol.  Survey,  1909,  p.  751. 


142 


PEGMATITES  AND  ASSOCIATED  ROCKS  OF  MAINE. 


motor  to  spark.  Much  of  the  sheet  mica  used  in  electrical  apparatus  is  first  made  up 
into  large  sheets  of  mica  board  or  micanite.  In  this  form  it  is  available  for  use  in  most 
of  the  purposes  for  which  ordinary  sheet  mica  can  be  used.  It  can  be  bent,  rolled, 
cut,  punched,  etc.  Bending  is  accomplished  during  baking,  or  by  heating  to  soften 
the  shellac  used  in  the  manufacture  of  the  mica  board.  Insulation  for  commutators 
is  generally  cut  from  “ amber”  mica  board. 

Scrap  mica,  or  mica  too  small  to  cut  into  sheets,  and  the  waste  from  the  manufac- 
ture of  sheet  mica  are  used  in  large  quantities  commercially.  The  greater  part  is 
ground  for  the  manufacture  of  wall  papers,  lubricants,  fancy  paints,  molded  mica  for 
electrical  insulation,  etc.  Ground  mica  applied  to  wall  papers  gives  them  a silvery 
luster.  When  mixed  with  grease  or  oils  mica  forms  an  excellent  lubricant  for  axles 
and  bearings.  Mixed  with  shellac  or  special  compositions,  ground  mica  can  be 
molded  into  desired  forms,  and  is  used  in  insulators  for  wires  carrying  high  potential 
currents.  Ground  mica  for  use  in  molded  mica  for  insulation  purposes  should  be  free 
of  metallic  minerals.  For  lubrication  purposes  it  is  necessary  that  gritty  matter  be 
eliminated,  either  after  grinding  or  by  using  only  pure  mica  for  grinding.  For  wall 
papers  and  brocade  paints  a ground  mica  with  a high  luster  is  required.  This  is  best 
obtained  by  using  a clean  light-colored  mica  and  grinding  under  water. 

Coarsely  ground  or  bran  mica  is  used  to  coat  the  surface  of  composition  roofing 
material,  especially  that  manufactured  by  the  Western  Elaterite  Roofing  Company, 
of  Denver,  Colo.  The  mica  serves  the  purpose  of  keeping  the  material  from  sticking 
when  rolled  for  shipping  or  storage. 

In  the  Western  States  the  dry  process  is  the  common  practice  in  grinding  mica,  but 
in  the  mica  regions  of  the  Eastern  States  the  greater  part  of  the  mica  is  ground  under 
water.  In  dry-grinding  machines  the  mica  is  pulverized  by  the  beating  action  of 
teeth  or  bars  on  cylinders  revolving  at  a high  rate  of  speed.  In  wet-grinding  machines 
the  mica  is  beaten  and  torn  under  water  by  teeth  or  spikes  mounted  in  wheels  or  cyl- 
inders revolving  at  a comparatively  slow  rate  of  speed.  The  capacity  of  the  dry- 
grinding machines  or  pulverizers  is  considerably  greater  than  that  of  the  wet-grinding 
machines.  The  dust  of  fine  mica  scales  from  the  pulverizers  is  often  a cause  of  annoy- 
ance to  workmen  around  the  mills,  as  it  is  very  irritating  to  the  throat  and  lungs  when 
breathed.  It  is  claimed  that  mica  ground  under  water  is  better  than  that  ground  dry. 
Some  consumers  demand  the  wet-ground  mica,  claiming  a greater  purity  and  more 
brilliant  luster.  It  is  possible  that  the  same  effect  could  be  obtained  by  thoroughly 
washing  dry-ground  mica  and  floating  the  product. 

PRICES  AND  PRODUCTION. 

The  following  statements  in  regard  to  the  price  of  mica  are  also 
quoted  from  Sterrett’s  report: 

The  average  price  of  sheet  mica  in  the  United  States  during  1908,  as  deduced  from 
the  total  production,  was  24.1  cents  per  pound,  as  compared  with  33  cents  per  pound 
in  1907  and  with  17.7  cents  in  1906.  The  average  prices  per  pound  of  sheet  mica  as 
reported  in  the  production  from  several  States  were  as  follows:  Virginia,  44.2  cents; 
South  Carolina,  35.7  cents;  South  Dakota,  33.3  cents;  Alabama,  24  cents;  North  Caro- 
lina, 19.1  cents.  These  average  values  vary  greatly  from  year  to  year,  a result  caused 
in  part  by  variation  between  the  proportion  of  rough  and  trimmed  sheet  mica  sold  by 
the  producers  and  in  part  by  variation  in  the  size  of  sheet  produced. 

The  prices  of  several  sizes  of  selected  mica  quoted  in  the  price  list  of  a large  mica 
company  of  New  York  during  1908  were  as  follows: 


Prices  per  pound  of  selected  sizes  of  sheet  mica  at  New  York  in  1908. 


2 by  2 inches 

2 by  3 inches 

$0.87 

1. 10 

3 by  4 inches 

4 by  6 inches 

2 by  5 inches 

1. 70 

6 by  8 inches 

3 by  3 inches „ 

$3.  25 
4.  75 
6.  75 


TOURMALINE. 


143 


In  most  years  the  importations  of  mica  into  the  United  States  are 
largely  in  excess  of  the  domestic  production  in  value.  They  come 
mainly  from  India  and  Canada. 

TOURMALINE. 

Chemical  and  'physical  properties. — Tourmaline  is  a complex  silicate 
of  boron  and  aluminum  containing  various  amounts  of  either  magne- 
sium, iron,  or  the  alkali  metals.  The  form  of  the  more  perfect  crystals 
is  commonly  that  of  a three-sided  prism,  the  sides  of  the  prism  usually 
being  striated  and  channeled  (PI.  XV).  In  many  crystals  the  three- 
sided  form  is  somewhat  modified  by  the  combination  with  it  of  a hex- 
agonal prism.  The  latter  is  usually  subordinate  and  has  the  effect  of 
merely  somewhat  rounding  the  angles  of  the  triangular  prism.  Many 
crystals  are  terminated  by  three  planes  forming  a low  pyramid,  but 
in  others  the  number  of  terminal  planes  is  very  large.  The  hardness 
(7  to  7.5)  is  slightly  greater  than  that  of  quartz.  There  is  no  well- 
defined  cleavage. 

The  mineral  exhibits  a great  variety  of  colors,  ranging  from  black 
through  brownish-black  and  blue-black  to  blue,  green,  red,  pink,  and 
colorless.  The  red  varieties  go  under  the  name  of  rubellite;  the  blue 
varieties  are  known  as  indicolite  and  the  colorless  as  achroite.  A 
crystal  may  be  green  at  one  end  and  red  at  the  other  or  in  cross 
section  may  show  a blue  center,  then  a zone  of  red,  and  then  one  of 
green.  Some  of  the  crystals  from  Paris,  Oxford  County,  grade  from 
white  at  one  termination  to  emerald  green,  then  light  green,  then 
pink,  and  finally  are  colorless  at  the  other  termination.  The  color  is 
dependent  on  the  chemical  composition,  the  green,  blue,  pink,  and 
colorless  varieties  generally  being  rich  in  lithium  and  manganese  and 
the  dark  opaque  varieties  being  particularly  rich  in  iron.  The  color 
in  the  transparent  varieties  varies  with  the  direction  in  which  the 
light  penetrates  the  gem;  thus  a crystal  which,  when  viewed  from 
the  side,  is  a transparent  green,  may  be  opaque  or  yellow-green  when 
viewed  along  the  length  of  the  prism.  Because  of  this  property  of 
dichroism,  as  it  is  called,  it  is  usually  necessary  in  cutting  gem  tour- 
malines to  make  the  11  table”  of  the  stone  parallel  to  the  long  axis  of 
the  crystal.  Another  distinctive  quality  of  the  mineral  is  that  it 
becomes  electrified  when  warmed  slightly  and  is  then  capable  of 
picking  up  ashes,  small  scraps  of  paper,  etc. 

Occurrence. — Tourmaline  occurs  in  small  crystals  in  a great  variety 
of  rocks  and  may  be  either  an  original  crystallization  or  the  result  of 
metamorpliic  processes.  Large  crystals  and  those  which  are  of  gem 
value  occur  only  in  the  pegmatite  deposits.  The  black  varieties  occur 
almost  exclusively  in  the  solid  pegmatite  associated  with  quartz  and 
feldspar  and  without  any  regularity  in  arrangement.  The  black 
varieties  may  contain  from  3 to  nearly  20  per  cent  of  oxides  of  iron 


144 


PEGMATITES  AND  ASSOCIATED  ROCKS  OP  MAINE. 


and  must  be  carefully  separated  from  feldspar  which  is  to  be  used  for 
pottery  purposes.  The  colored  varieties  occasionally  are  found  also 
in  the  solid  pegmatite,  as  at  the  Newry  mine  (p.  76),  but  where  occur- 
ring in  this  way  seldom  yield  much  gem  material  because  of  the  diffi- 
culty of  removing  them  unfractured  from  their  matrix.  The  colored 
tourmalines  showing  the  greatest  perfection  in  crystal  form  and  yield- 
ing most  of  the  gem  stock  occur  in  pockets  in  the  coarse  pegmatite 
bodies.  For  a detailed  description  of  their  mode  of  occurrence  the 
reader  is  referred  to  the  description  of  Mount  Mica  (pp.  81-93). 

Outside  of  Maine  gem  tourmalines  are  produced  in  the  United 
States  in  important  amounts  only  in  Connecticut  and  California. 
Abroad  they  are  found  in  Brazil,  in  the  Ural  Mountains,  and  in  Ceylon. 

Mining , 'prices , etc. — Mount  Mica  in  Paris  and  Mount  Apatite  in 
Auburn  are  the  only  localities  where  systematic  mining  for  tourma- 
lines is  now  being  carried  on,  although  a few  gem  tourmalines  are 
occasionally  found  at  certain  of  the  feldspar  quarries.  The  quarries 
have  been  described  in  the  detailed  locality  descriptions.  In  general, 
the  excavation  must  proceed  with  great  caution;  the  drilling  must  be 
done  in  a most  careful  manner,  much  of  it  by  hand ; and  heavy  charges 
of  explosives  must  be  avoided  because  of  the  liability  of  shattering 
valuable  gem  material. 

Most  of  the  gem  tourmalines  now  mined  in  Maine,  when  not  pre- 
served for  museum  purposes,  are  cut  within  the  State  by  lapidaries 
whose  workmanship  is  said  often  to  equal  that  of  the  best  New  York 
cutters.  The  size  and  general  character  of  the  finest  gems  which 
have  been  cut  is  described  in  the  discussion  of  Mount  Mica.  The 
great  bulk  of  the  cut  tourmalines  marketed  are,  however,  below^B 
carats  in  size.  Rubellites  and  stones  of  a color  approaching  an  erne] 
aid  green  are  the  most  valuable. 

The  prices  obtained  in  Maine  are  higher  than  those  current  in  New 
York  City,  because  most  are  sold  at  retail  to  residents  of  the  State  or  to 
summer  tourists  and  have  an  enhanced  value  as  souvenirs.  Rubel- 
lites  and  emerald-green  varieties  bring  at  retail  from  $8  to  $20  per 
carat.  The  indicolite  and  olive-green  varieties  bring  from  $6  to  $18 
a carat. 

BERYL. 

CHEMICAL  AND  PHYSICAL  PROPERTIES. 

Under  the  name  beryl  are  included  the  opaque  beryl  found  in 
nearly  all  the  pegmatite  dikes  and  the  much  rarer  gem  varieties, 
emerald,  aquamarine,  golden  beryl,  and  caesium  beryl.  In  chemical 
composition  beryl  is  a silicate  of  beryllium  and  alumina  having  the 
general  formula  of  Be3Al2Si6018  or  3Be0.Al203.6Si02,  but  with  the 
beryllium  oxide  replaced  in  some  varieties  by  soda,  lithia,  or  calcium 
oxide.  The  mineral  has  a hardness  of  7J  to  8;  that  is,  it  can  not 


BERYL. 


145 


be  scratched  with  a knife.  The  color  varies  from  emerald  green 
through  pale  green,  light  blue,  and  golden  yellow  to  white  and  pale 
pink.  The  crystals  are  generally  hexagonal  prisms,  many  of  them 
striated  vertically,  and  most  of  them  terminated  by  a single  flat 
plane  at  right  angles  to  the  long  axis  of  the  prism.  Some  pyramidal 
terminations  also  occur.  There  is  no  marked  cleavage,  only  an 
imperfect  one  parallel  to  the  basal  planes.  Beryl  is  fusible  only  with 
difficulty  and  is  not  attacked  by  acids. 

OPAQUE  BERYL. 

The  commoner  varieties  of  beryl  are  fight  blue  or  green  in  color, 
and  are  opaque,  though  portions  of  some  crystals  are  transparent 
and  may  even  yield  gems.  Opaque  crystals  are  quite  common  in 
most  of  the  coarser  pegmatite  deposits  of  Maine,  where  they  occur  as 
more  or  less  regular  prisms  embedded  in  the  solid  pegmatite.  Some 
of  these  reach  remarkable  dimensions:  one  found  in  the  Maine  Feld- 
spar Company’s  quarry  at  Mount  Apatite  in  Auburn  was  described 
as  having  a diameter  equal  to  that  of  a hogshead.  One  from  the 
Noyes  gem  mine  in  Greenwood,  Oxford  County,  was  so  large  that  a 
man  could  barely  reach  around  it  with  his  arms.  From  Acworth, 
N.  H.,  one  crystal  6J  feet  long  and  another  estimated  to  weigh  over 
2\  tons  were  quarried.  A peculiar  beryl  from  Auburn  is  described 
by  Kunz  as  follows : a 

In  the  state  cabinet  in  Albany,  N.  Y.,  is  a curious  beryl  found  by  S.  C.  Hatch  at 
Auburn,  Maine.  It  is  of  imperfect  structure  and  broken  diagonally  across,  showing  the 
structure  to  advantage.  It  is  8f  inches  (30  centimeters)  high,  8f  inches  (22  centi- 
liters) wide,  and  has  50  different  layers,  25  of  beryl,  the  remaining  25  of  albite, 
ouartz,  and  muscovite.  All  the  corners  of  the  hexagonal  prism  are  carried  out  in 
full,  giving  the  beryl  an  asteriated  appearance  and  making  it  a striking  and  interesting 
specimen. 

The  opaque  varities  of  beryl  are  of  little  commercial  value,  though 
prized  for  museum  collections  when  they  show  perfect  crystal  forms. 

EMERALD. 

Transparent  beryl  of  deep-green  color  is  the  gem  emerald,  but  it 
must  not  be  confused  with  the  oriental  emerald,  which  is  a green 
variety  of  corundum.  Emeralds  are  of  rare  occurrence  in  the  peg- 
matite deposits  of  Maine.  One  crystal  of  light  grass-green  color 
embedded  in  quartz  was  observed  by  the  writer  at  the  Dunton  gem 
quarry  in  Newry,  Oxford  County.  It  was  a prism  half  an  inch  across 
and  lj  inches  long  but  was  so  badly  fractured  as  to  be  valueless 
for  gems.  Parker  Cleveland  h mentions  having  seen  several  emer- 
alds from  Topsham,  Sagadahoc  County,  of  a lively  green  color  and 

a Kunz,  G.  F.,  Gems  and  precious  stones,  pp.  91-92. 

& Mineralogy  and  geology,  1822. 

63096°— Bull.  445—11 10 


146 


PEGMATITES  AND  ASSOCIATED  ROCKS  OF  MAINE. 


comparable  in  beauty  to  the  Peruvian  emeralds,  but  none  are  now  in 
the  museums  and  none,  so  far  asythe  writer  knows,  have  since  been 
found.  In  the  United  States  emeralds  are  found  in  important  quan- 
tities only  in  North  Carolina.  Abroad  they  are  obtained  in  Colombia, 
the  Urals,  Austria,  and  upper  Egypt. 

AQUAMARINE. 

The  light-blue  to  sky-blue  and  light-green  transparent  varieties  of 
beryl  known  as  aquamarine  are  more  abundant  than  any  of  the  other 
gem  varieties  of  beryl  found  in  Maine,  and  specimens  of  remarkable 
size  and  beauty  have  been  obtained.  The  prismatic  crystals  lie  in 
various  positions  in  the  solid  pegmatite  masses  and  are  more  com- 
rhonly  associated  with  quartz  than  with  the  other  constituents. 
Few  of  them  occur  in  pockets.  Their  position  in  the  solid  ledge 
renders  it  difficult  to  obtain  the  crystals  without  more  or  less  frac- 
turing. Some  few  crystals  come  from  quarries  which  are  worked 
primarily  for  feldspar  or  for  tourmalines,  but  the  principal  supply, 
like  that  of  golden  beryl,  is  obtained  by  gem  collectors  who  work 
small  prospects,  using  hand  drills  and  light  blasts  of  powder. 

Most  of  the  gem  material  has  come  from  Oxford  County.  Some 
has  been  obtained  from  what  is  known  as  the  Emmons  mine  in  the 
southwestern  part  of  Greenwood,  from  Frenchs  Mountain  in  Albany, 
Sugar  Hill  in  Stoneham,  and  Lovell,  Bethel,  and  other  towns.  A fine 
sea-green  aquamarine  weighing  about  7 carats  was  found  near  Sum- 
ner. Recently  some  good  gems  have  been  obtained  on  the  Dudley 
farm  in  Buckfield. 

The  price  obtained  at  retail  for  the  cut  stones  ranges  from  $4  to 
$15  per  carat  for  perfect  stones,  depending  on  the  size  and  color. 
Most  of  the  stones  now  obtained  in  Maine  are  cut  and  marketed 
within  the  State. 

GOLDEN  BERYL. 

Beautiful  transparent  golden-yellow  beryls  have  been  obtained  in 
the  pegmatites  at  various  points  in  Oxford  County,  at  Edgecomb 
Mountain  in  Stoneham,  in  Albany,  and  recently  good  gem  material 
of  a straw  yellow  has  been  obtained  from  the  west  side  of  Speckled 
Mountain  in  Peru.  They  are  mined  sporadically  by  gem  collectors, 
mostly  from  small  prospects.  The  retail  prices  obtained  for  flawless 
cut  stones  of  this  variety  vary  from  $10  to  $25  per  carat,  depending 
upon  the  size  and  color.  Nearly  all  that  are  found  are  sold  to  resi- 
dents or  to  visitors,  and  as  native  Maine  gems  command  a higher  price 
than  they  would  in  the  general  markets. 


TOPAZ. 


147 


CAESIUM  BERYL. 

A colorless  to  bluish-white  or  pinkisli-white  variety  of  beryl  con- 
taining a small  percentage  (1.66  per  cent  to  3.6  per  cent)  of  oxide  of 
caesium  was  first  discovered  in  Hebron,  Oxford  County,  but  has  since 
been  found  to  occur  at  a number  of  other  pegmatite  localities  in  the 
western  part  of  the  State,  notably  at  Mount  Mica  in  Paris,  at  the 
Dudley  farm  in  Buckfield,  Oxford  County,  and  at  the  feldspar  quarry 
of  Mr.  A.  R.  Berry  in  Poland,  Androscoggin  County.  Generally  it 
occurs  in  somewhat  irregular  masses  in  the  solid  pegmatite,  but  in 
some  occurrences  shows  regular  crystal  forms.  When  cut  it  makes  a 
stone  of  high  brilliancy  which  as  a night  stone  is  considered  by  some 
to  be  superior  to  many  diamonds.  It  is  valued  chiefly  because  of  its 
resemblance  to  the  diamond.  Flawless  cut  stones  of  moderate  sizes 
sell  at  retail  at  present  at  from  $5  to  $20  a carat. 

TOPAZ. 

Topaz  is  a silicate  of  alumina  containing  fluorine  and  having  about 
the  composition  Al12Si6O25F10.  It  may  be  colorless,  straw  yellow,  or 
wine  yellow,  or  may  show  faint  tints  of  gray,  green,  blue,  or  red.  Its 
hardness  is  8,  and  it  is  thus  capable  of  scratching  quartz.  It  is  also 
much  heavier  than  quartz,  having  a specific  gravity  of  3.4  to  3.65. 
The  mineral  belongs  to  the  orthorhombic  system  and  its  crystals  are 
usually  prismatic  in  form,  with  one  end  terminated  by  crystal  faces. 
It  possesses  a perfect  cleavage  at  right  angles  to  the  prism  axis. 
Transparent  smoky  quartz  is  frequently  called  smoky  topaz,  and  the 
so-called  Spanish  topaz  is  simply  smoky  quartz  heated  until  it 
assumes  a yellow  color.  Clear,  colorless  quartz  is  also  sometimes 
sold  under  the  name  of  topaz. 

So  far  as  known  to  the  writer,  topaz  in  any  considerable  amounts 
has  been  found  in  Maine  only  at  Harndon  Ilill  in  Stoneham,  Oxford 
County.  (See  p.  100.)" 


INDEX, 


A.  Page. 

Abrasives,  feldspar  for 129 

quartz  for 135 

Alaska,  graphic  granite  from 24 

Albany,  pegmatites  in 70 

Amblygonite,  occurrence  and  character  of 88 

Amethysts,  occurrence  and  character  of 102, 138 

Andover,  pegmatites  in 71 

Androscoggin  County,  pegmatites  in 46-61 

Apatite,  definition  of 16 

occurrence  and  character  of.  52-53, 58, 60, 88, 101 

Appleton,  rocks  near 69 

Aquamarines,  occurrence  and  character  of. . 99, 146 

A-structure,  explanation  of 139 

Auburn,  graphic  granite  in, plate  showing..  22 

pegmatites  in 11, 46-59 

plate  showing 10 

Auburn  Falls,  pegmatites  at . . 46 

Auburn  reservoir,  pegmatites  near ' 46-47 

B. 

Bay  Point  Peninsula,  pegmatites  on 108-109 

Beech  Hill  mine,  description  of 104-105 

mica  of 104-105,141 

Bennett  prospect,  mica  at 70 

Berry,  A.  R.,  quarry  of 59-61 

Beryl,  definition  of 16 

occurrence  and  character  of 52, 60, 

70, 78, 92, 98-99, 101, 144-147 
See  also  particular  varieties. 

Beryllonite,  definition  of 16 

occurrence  and  character  of 99-100 

Biotite,  definition  of 17 

See  also  Mica. 

Black  Mountain  mine,  description  of 95-97 

mica  in 95-96, 140 

Boothbay  Harbor,  pegmatites  near 12,14, 

19,35,64-70 

pegmatites  near,  figure  showing 14 

Brunswick,  pegmatites  in 12, 13, 61-62 

Buckfield,  pegmatites  in 71 

Bygden,  A.,  on  graphic  granite 40 

C. 

Caesium  beryl,  occurrence  and  character  of. . . 147 

Calcite,  definition  of 16 

occurrence  and  character  of 68-69 

Calkins,  F.  C.,  on  graphic  granite 24 

Cathance,  pegmatites  near 112-114 

Cavities,  gems  in 32-33 

See  also  Miarolitic  cavities. 

Chemical  apparatus  ware,  quartz  for 135-136 

Citrine,  occurrence  and  character  of 137 

Cobble  Hill,  pegmatites  near — 78-79 


Page. 

Colombite,  occurrence  and  character  of 101 

Contact-metamorphic  effects,  occurrence  and 

character  of 33-35 

Crocker  Hill,  pegmatites  at  and  near 11,79-81 

Crystallization,  differences  in,  effects  of.  28-36, 45-46 

temperature  of,  effect  of 36-39 

Cumberland  County,  pegmatites  in 61-63 

Cumberland  Mills,  pegmatites  at 62-63 

Cushman,  A.  S.,  on  feldspar  as  fertilizer 130 

D. 

Dale,  T.  N.,  on  fluidal  cavities .. 21 

Danville  Corners,  pegmatites  near 47-48 

Danville  Junction,  pegmatites  near 48-49 

Deer  Hill,  amethysts  at 102 

Diabase  dike,  view  of 98 

Dikes.  See  Pegmatite  dikes. 

Diorite,  lenses  of,  plate  showing 12 

Dunton  tourmaline  mine,  description  of 76-78 

E. 

Edgecomb,  pegmatites  in 63-64 

Electrical  apparatus,  mica  for 141 

Emerald,  definition  of 17 

occurrence  and  character  of 145-146 

Emmons,  W.  H.,  on  Mount  Mica 36,83 

Eutectics,  importance  of,  in  rock  forma- 
tion  39-43,46 

F. 

Feldspar,  analyses  of 51,106,123,124 

commercial  availability  of  deposits  of..  126-127 

composition  of 119-125 

definition  of 17 

impurities  in . 127 

intergrowths  of,  with  quartz,  plate  show- 
ing  24,124 

milling  of 127-128 

mining  of 125-126 

cost  of. 126 

prices  of 130-131 

production  of 132 

quarries  of...  51,63-64,72-73,86,105-108,110-117 

uses  of 129-131 

Feldspar  brushes,  occurrence  and  character  of.  23'-25 

Ferrosilicon,  quartz  for 135 

Fertilizer,  feldspar  for 130 

Field  work,  extent  of 9 

Fisher,  J.  A.,  quarry  of 112-113 

quarry  of,  graphic  granite  from , analyses  of  124 
Fluidal  cavities,  bands  of,  plate  showing 18 


149 


150 


INDEX. 


Page. 

Fluidal  cavities,  figures  showing 20, 77 

occurrence  and  character  of 19-21,77 

Fluorine  minerals,  distribution  of 43 

Fluorine  phase,  description  of 21 

Foliates,  definition  of 11 

origin  of 11-13 

pegmatite  intrusions  in 11-13 

French  Mountain,  beryls  at 70 

Garnet,  definition  of 17 

occurrence  and  character  of Passim  52-119 

Gaseous  constituents,  effect  of,  in  crystalliza- 
tion  30-32,45 

effect  of,  on  viscosity 30-36 

Gems,  occurrence  and  character  of 26-27, 

52, 53, 55-56, 58, 60-61, 74, 89-92, 98-102, 116 
See  also  Tourmalines. 

Geology,  account  of 10-46 

Georgetown,  pegmatites  in 105-109 

pegmatites  in,  plate  showing 10 

Georgetown  Center,  pegmatites  at 105 

Glass,  feldspar  for 129 

Gneiss,  flow  structure  in,  plate  showing 12 

foliation  of 12-13 

Golden  beryl,  occurrence  and  character  of 146 

Grain,  variations  in. . > * 10, 22 

Granite,  distribution  of,  map  showing Pocket 

Goldings  quarry,  feldspar  at 105-108 

intergrowths  at,  plate  showing 120 

Granite,  pegmatite  intrusions  in 13-15 

figure  showing 14 

Grant  quarry,  pegmatites  in 61 

Graphic  granite,  analyses  of 124 

composition  of 40-42, 124 

diagram  showing 40 

occurrence  and  character  of 22-23, 

118-119,124-125 

plate  showing 22 

Graphite  mine,  rocks  at 11 

Greenwood,  pegmatites  iru 71-72 


H. 

Hamlin,  E.  S.,  Mount  Mica  deposits  found  by.  81 


work  of 82,83,85 

Hamlinite,  occurrence  and  character  of 101-102 

Hancock  County,  pegmatites  in 63 

Harndon  Hill,  gems  at 100-102 

Hebron,  pegmatites  in 72-76 

structure  in,  figure  showing 73 

Hibbs  farm,  quarry  on 72-74 

quarry  on,  mica  in 140 

section  on,  figure  showing 73 

Hinckleys  Landing,  pegmatites  at 105 

I. 

Iddings,  J.  P.,  on  crystallization 30,45 

Igneous  foliates,  nature  of 12 

Injection  gneiss,  occurrence  of 11 

plate  showing 10 

Intergrowths,  occurrence  and  character  of. . . 22-26, 

42-43 

Intrusives,  forms  of 35 

Iron  minerals,  injurious  effects  of 127 


J.  Page. 

Johanssen,  H.  E.,  on  graphic  granite 40 

K. 

Keewaydin  Lake,  rocks  near 15,98 

Kennebec  Point,  pegmatites  in 109 

Knopf,  Adolph,  on  graphic  granite 24 

Kunz,  G.  F.,  on  beryl 145 

on  Harndon  Hill 100 

Kunzite,  occurrence  and  character  of 71 

L. 

Larsen,  E.  S.,  and  Wright,  F.  E.,  on  quartz 

crystallization 36-39,45-46 

Lee,  L.  A.,  aid  of 98 

Lepidolite,  definition  of 17, 

occurrence  and  character  of 52 

57-58,77,87, 138-139 

Lewiston,  pegmatite  from 46 

pegmatite  from,  photomicrograph  of 10 

Lime-soda  feldspars,  composition  of 120-123 

qualities  of 121-123 

Lincoln  County,  pegmatites  in 63-70 

Lithium  phase,  description  of 21 

distribution  of 43 

M. 

McKown  Point,  pegmatites  at 65, 69 

McMahons  Island,  pegmatites  on,  plate 

showing 10 

Maine,  cooperation  of 9 

map  of  part  of Pocket 

Maine  Feldspar  Co.,  quarries  of 50-54, 115 

quarries  of,  pegmatites  in 53 

Map  of  part  of  Maine Pocket 

Metamorphism,  occurrence  and  character  of. . 11-12 
See  also  Contact  metamorphism. 

Miarolitic  cavities,  occurrence  and  character 

of 32-33 

Mica,  injurious  effects  of 127 

intergrowths  of,  plate  showing 120 

occurrence  and  character  of 26, 

Passim  51-119,138-139 

types  of 138-139 

wedge  structure  in,  plate  showing 138 

See  also  Muscovite. 

Microcline,  composition  of 119 

Mills  quarry,  description  of 76 

Mineral  composition,  character  of 15-22 

effects  of,  on  crystallization 28-29,45 

Mineralizers,  definition  of 32 

Minerals,  effect  of,  on  crystallization 29-30, 45 

list  of 16-18 

proportions  of 18,28-29 

Minot,  pegmatites  in 59 

Montana,  graphic  granite  from 24 

Mount  Apatite,  gems  at 49-50 

pegmatites  at 49-50 

quarries  on 50-59 

Mount  Ararat,  quarries  on 110-112, 117-119 

Mount  Mica,  gems  from 89-92 

gems  from,  plates  showing 88,90 

mine  at,  description  of 81-93 

plates  showing 82, 84 

pegmatite  pockets  at,  plates  showing 26,86 

structure  at,  figure  showing 84 


INDEX. 


151 


Page. 

Mount  Rubellite,  gems  at 74 

Muscovite,  defects  in 139-140 

defects  in,  plate  showing 138 

manufacture  of 140-141,142 

mining  of 140-141 

prices  of 142 

production  of 143 

occurrence  and  character  of Passim  51-112, 

139-141 

uses  of 141-142 

See  afso  Mica. 

Muscovite  phase,  description  of 22 

N. 

Newry,  pegmatites  in 76-78 

New  Mexico,  graphic  granite  from 24 

North  Topsham,  feldspar  quarry  at 116-117 

Norway,  pegmatites  in 78-79 

rocks  at,  plate  showing 18 

O. 

Orthoclase,  composition  of 119 

Oxford  County,  pegmatites  in 70-105 

P. 

Paints,  quartz  for 134 

Paris,  pegmatites  in 33-34,79-93 

schists  in,  structure  of,  plate  showing 

structure  in,  figures  showing 19,84 

Pegmatite,  age  of 14-15 

character  of 15-27 

definition  of 10 

distribution  of 10, 43-45 

map  showing Pocket 

fluorine  phase  of 21 

lithium  phase  of 21 

muscovite  phase  of 22 

origin  of 27-46 

photomicrographs  of 10, 24, 26, 34, 120, 124 

quartzose  phase  of 18-19 

figure  showing 19 

relation  of,  to  bordering  rocks 10-15 

schist  fragments  in 35-36 

sodium  phase  of 21 

texture  of . 22-27 

Pegmatite  dikes,  structure  of 11, 13 

structure  of,  figure  showing 11 

Pemaquid  Point,  rocks  at,  plate  showing 10 

Penobscot  Bay  quadrangle,  rocks  in 15, 44 

Perry  Basin,  rocks  near 15 

Peru,  pegmatites  in 93 

Pingree,  C.  P.,  mica  prospect  of 70 

Plagioclases,  composition  of 120-123 

Pockets,  gem-bearing,  occurrence  and  charac- 
ter of 27, 

53, 58-59, 71-72, 74, 82-86, 89, 116 

views  of 26,86 

Poland,  pegmatites  in 59-61 

Potash-soda  feldspars,  composition  of 119-120 

Pottery,  feldspar  for 127, 128, 129 

quartz  for 138 

Poultry  grit,  feldspar  for 129 

Pulsifer,  P.  P.,  quarry  of 56-59 


Q.  Page. 

Quartz,  crystallization  of,  temperature  of. . 36^39 

definition  of 17 

intergrowths  of,  with  feldspar,  plate 

showing 24,124 

milling  of . 133-134 

occurrence  and  character  of. . Passim  50-119, 133 

prices  of 137 

production  of. 136 

uses  of 134-136 

vein  of,  view  of 98 

Quartz,  rose, occurrence  and  character  of...  137-138 
Quartz,  smoky,  occurrence  and  character  of.  137 
Q,uartzose  phase,  description  of 18-19 

R. 

Rare  minerals,  effect  of,  on  crystallization..  29-30 


Raoult’s  law,  statement  of 31 

Rockland  quadrangle,  rocks  in 44 

Rose  quartz,  occurrence  and  character  of. . 137-138 

Ruling,  defects  in  mica  due  to 139-140 

Rumford,  pegmatites  in 26,35,93-97 

Rumford  Falls,  pegmatites  at  and  near.  34, 35, 94-95 
schist  at,  feldspar  in,  plate  showing 34 

S. 

Sagadahoc  County,  pegmatites  in 105-119 

St.  George  River,  rocks  on 12 

Schaller,  W.  T.,  on  California  pegmatites..  42 

Schists,  foliation  of 11-12 

structure  of,  plate  showing 34 

Scouring,  feldspar  for 129 

quartz  for 134 

Silicon,  quartz  for 135 

Small  Point  feldspar  quarry,  description  of. . 108 

Sodium  phase,  description  of 21 

South  Glastonbury,  Conn.,  quartz  vein  at, 

view  of 98 

Southport,  rocks  near 14 

South  Waterford  mica  prospect,  description 

of 103-104 

Spanish  topaz,  nature  of 137,147 

Spence  Hills,  pegmatites  in 98 

Spodumene,  definition  of 18 

fluidal  cavities  in 77,88 

figure  showing 77 

Spence  Point,  pegmatites  near 66 

Standish,  pegmatites  in 98 

Sterrett,  D.  B.,  on  mica 141-142 

Stoneham,  diabase  dike  in,  plate  showing  ...  98 

pegmatites  in 98-102 

Stoves,  mica  for 141 

Stow,  pegmatites  in 102 

Streaked  Mountain,  pegmatites  of 35-36,74-75 

Sugar  Hill,  gems  at 99-100 

Sweden,  graphic  granite  from 125 

Syenite  porphyry,  occurrence  and  character 

of 69 

T. 

Teeth,  artificial,  feldspar  for 129 

Texture,  photomicrograph  showing 10 

variations  in, . , 10 


152 


INDEX. 


Page. 

Todds  Bay,  feldspar  quarry  near 105-108 

Topaz,  definition  of 18 

occurrence  and  character  of 100, 147 

Topsham,  feldspar  and  quartz  at,  plate 

showing 24 

pegmatites  in 12,23,41,42,109-119 

plate  showing 26 

Tourmaline,  definition  of 18 

occurrence  and  character  of Passim  50-119, 

143-144 

Tourmalines,  gem,  definition  of 18 

occurrence  and  character  of 49, 

52,58, 60, 71, 72, 78, 81-92, 96, 144 

mining  of 144 

prices  of 144 

views  of 88,90 

Towne,  J.  S.,  quarry  of 55-56 


Page. 

Trenton  Flint  and  Spar  Co.,  mill  of. 117 

Tubbs  Ledge,  gems  at 78 

Turner,  E.  Y.,  quarries  of 54r-55 

V. 

Viscosity,  effects  of  gas  on 30-36 

Vogt,  J.  H.  L.,  on  graphic  granite 39-40,42 

W. 

Waterford,  pegmatites  in 102-105 

Westbrook,  pegmatites  in 62-63 

Willes,  G.  P.,  quarry  of 115-116 

Willes,  William,  quarry  of. 113-114 

Woodside  quarry,  pegmatites  in 13,61 

Wright,  F.  E.,  and  Larsen,  E.  S.,  on  quartz 

crystallization 36-39, 45-46 


o 


